Patent Publication Number: US-2009231625-A1

Title: Sending apparatus, receiving apparatus, control method of these apparatuses, and storage medium

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sending apparatus which sends image data, a receiving apparatus which receives image data, a control method of these apparatuses, and a storage medium. 
     2. Description of the Related Art 
     Conventionally, various methods for sending and receiving image data via a network are discussed as follows. When a sending apparatus sends image data to a receiving apparatus, the sending apparatus first transmits a call for sending the image data to the receiving apparatus. Then, when the call from the sending apparatus is received, the receiving apparatus determines whether it is in a receivable status, and notifies the sending apparatus that the receiving apparatus is in the receivable status or is in a non-receivable status according to a result of the determination. When a notification that the receiving apparatus is in the receivable status is received therefrom, the sending apparatus sends the image data to the receiving apparatus. 
     Alternatively, when a notification that the receiving apparatus is in the non-receivable status is received therefrom, the sending apparatus cannot send the image data to the receiving apparatus. The receiving apparatus is in the non-receivable status when, for example, it is in the middle of data communication with another apparatus which is different from the sending apparatus that transmitted the call. 
     When the image data cannot be sent, a user at the sending apparatus side has to make contact by telephone with a user at the receiving apparatus side and transmits the call again after confirming whether the receiving apparatus has shifted to the receivable status, or the sending apparatus needs to automatically repeat retransmission of the call to the receiving apparatus. 
     To cope with such a situation, Japanese Patent Application Laid-Open No. 2006-067045 discusses a following method. When a sending apparatus transmits a call for sending image data to a receiving apparatus, if the receiving apparatus is in a non-receivable status, the sending apparatus sends a recovery notification message to the receiving apparatus. The recovery notification message requests the receiving apparatus to notify the sending apparatus of recovery, when the receiving apparatus recovered from the non-receivable status to a receivable status. The receiving apparatus that received the recovery notification message will notify the sending apparatus of the recovery when the receiving apparatus recovers from the non-receivable status to the receivable status. Consequently, the sending apparatus can send the image data by retransmitting the call after receiving the notification from the receiving apparatus, so that contact by telephone and repeat of retransmission of the call as described above are not necessary. 
     However, the above described method of Japanese Patent Application Laid-Open No. 2006-067045 may cause a situation as described below. Even if the receiving apparatus would notify the sending apparatus that the receiving apparatus has shifted to the receivable status, the sending apparatus cannot immediately send the image data in a case where the sending apparatus is in a non-transmittable status at that moment (for example, in the middle of communicating with another apparatus). Further, when some time has elapsed after the sending apparatus becomes unable to send the image data, if the sending apparatus would attempt to send the image data again, the receiving apparatus might have already shifted to the non-receivable status again at that moment. In this case, the sending apparatus cannot send the image data as well. Thus, even if the receiving apparatus would notify the sending apparatus that the receiving apparatus has shifted to the receivable status by using the method of Japanese Patent Application Laid-Open No. 2006-067045, the sending apparatus may not immediately send the image data in some cases. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, a sending apparatus which sends image data includes a call unit configured to transmit a call to a receiving apparatus to send the image data, and a securing unit configured to secure a communication channel for sending the image data to the receiving apparatus until the receiving apparatus sends a notification that the receiving apparatus has shifted to a receivable status, if a response from the receiving apparatus to the call transmitted by the call unit indicates that the receiving apparatus is in a non-receivable status. 
     According to another aspect of the present invention, a receiving apparatus which receives image data includes a first notification unit configured to notify a sending apparatus, when the receiving apparatus receives a call from the sending apparatus for sending the image data and is in a non-receivable status, that the receiving apparatus is in the non-receivable status, a second notification unit configured to notify the sending apparatus that the receiving apparatus has shifted to a receivable status when the receiving apparatus has shifted to the receivable status after the first notification unit sent a notification, and a securing unit configured to secure, when the receiving apparatus has shifted to the receivable status, a communication channel for receiving the image data from the sending apparatus until the receiving apparatus again receives the call for sending the image data from the sending apparatus that received a notification from the second notification unit. 
     Further features and aspects of the present invention will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a block diagram illustrating a configuration of a multifunctional peripheral (MFP) according to an exemplary embodiment of the present invention. 
         FIG. 2  is an overall view of a communication system including a first MFP and a second MFP according to an exemplary embodiment of the present invention. 
         FIG. 3  illustrates a sending sequence of image data from a first MFP to a second MFP according to an exemplary embodiment of the present invention. 
         FIG. 4  is a flowchart illustrating operation steps of a first MFP according to an exemplary embodiment of the present invention. 
         FIG. 5  is a flowchart illustrating operation steps of a first MFP according to an exemplary embodiment of the present invention. 
         FIG. 6  illustrates an operation screen displayed on an operation panel unit according to an exemplary embodiment of the present invention. 
         FIG. 7  illustrates a sending sequence of image data from a first MFP to a second MFP according to an exemplary embodiment of the present invention. 
         FIG. 8  is a flowchart illustrating operation steps of a second MFP according to an exemplary embodiment of the present invention. 
         FIG. 9  is a flowchart illustrating operation steps of a second MFP according to an exemplary embodiment of the present invention. 
         FIG. 10  is a flowchart illustrating operation steps of a first MFP according to an exemplary embodiment of the present invention. 
         FIG. 11  illustrates an operation screen displayed on an operation panel unit according to an exemplary embodiment of the present invention. 
         FIG. 12  illustrates an address book according to an exemplary embodiment of the present invention. 
         FIG. 13  is a flowchart illustrating operation steps of a second MFP according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Various exemplary embodiments, features, and aspects of the invention will be described in detail below with reference to the drawings. 
       FIG. 1  is a block diagram illustrating a configuration of a multi-functional peripheral (MFP)  100  that functions as a sending apparatus or a receiving apparatus according to a first exemplary embodiment of the present invention. The MFP  100  includes a control unit  110  which controls operation of the entire apparatus, an operation panel unit  120 , and an external memory unit  130 , a printer unit  140  which prints an image onto a recording paper, and a scanner unit  150  which reads out an image on a document and input the image as image data. 
     An input/output unit  173  is connected to a local area network (LAN)  200  via a communication line  101 , and controls data communication with host computers and other MFPs on the LAN  200 . An input/output buffer  174  temporarily stores a page description language (PDL) data and various control commands that are input via the LAN  200 , or image data and various control commands that are sent from the MFP  100 . 
     A central processing unit (CPU)  163  controls operation of the entire control unit  110  by executing various programs stored in a program read-only memory (ROM)  175 . A random access memory (RAM)  169  is used as a work memory when calculation necessary for analysis of various control commands and processing of image data is performed. A non-volatile random access memory (NVRAM)  166  stores data that needs to be retained, even when the power of the MFP  100  is tuned off. 
     A control command interpretation unit  176  interprets a print control command received from the host computers on the LAN  200  with reference to information managed by a control command management table  168 . A PDL data interpretation unit  177  interprets PDL data received from the host computers. 
     An image object generation unit  178  generates various image objects. A bitmapped image rasterization unit  180  rasterizes the PDL data that the PDL data interpretation unit  177  has interpreted and the image object that the image object generation unit  178  has generated and generates bitmapped images. 
     An image compression/decompression unit  181  compresses and decompresses the bitmapped images that the bitmapped image rasterization unit  180  has generated. An image data printing unit  182  controls printing of the image data by a printer unit  140 . An image data sending unit  183  controls sending of the image data via the LAN  200 . An image data reading unit  184  controls reading of the images and generation of the image data by a scanner unit  150 . 
     A registered image management unit  185  registers and manages the bitmapped images generated by the bitmapped image rasterization unit  180  and images in a fixed format which are used in a form overlay function. A user management unit  186  manages user names, passwords and other information about users who are permitted to use the MFP  100  in a user information management table  167 . 
     A user authentication unit  187  performs a user authentication based on information that is input by a user via the operation panel unit  120 , and the information managed by the user management unit  186 . An image combining unit  188  combines images to be output from the printer unit  140 . An image data receiving unit  189  controls receipt of the image data via the LAN  200 . 
     A bitmapped image transfer unit  164  transfers the bitmapped images generated by the bitmapped image rasterization unit  180  to the printer unit  140  via a printer interface unit  165 . A printer control unit  141  provided in the printer unit  140  controls a printing operation in the printer unit  140 . 
     A bitmapped image receiving unit  170  receives the bitmapped images that are generated by the scanner unit  150  based on images on a document via a scanner interface unit  171 . A scanner control unit  151  provided in the scanner unit  150  controls scanning (reading the document) operation in the scanner unit  150 . 
     Information to be output from the operation panel unit  120  is transferred via a panel I/F unit  161  to the operation panel unit  120 . Also, information that the user inputs via the operation panel unit  120  is input via the panel I/F unit  161 , and notified to the CPU  163 . Various pieces of information about the image data and the MFP  100  are transferred via a memory I/F unit  162  to the external memory unit  130 , and stored within an external memory  130 . Each of the above described function units in the control unit  110  are interconnected via a system bus  172 . 
       FIG. 2  is an overall view of a communication system including the MFPs  210  and  220  which have similar configuration to that of the above described MFP  100 . The MFP  210  and the MFP  220  are communicably connected with each other via the LAN  200 . Here, a case where the MFP  210  functions as a sending apparatus and sends the image data to the MFP  220 , as well as the MFP  220  functions as a receiving apparatus and receives the image data from the MFP  210  is described. Each MFP performs call control for data communication based on a session initiation protocol (SIP), and sending and receiving the image data by executing facsimile communication according to requirements of Telecommunication Standardization Sector of International Telecommunication Union (ITU-T) Recommendations T.38. The SIP is a standardized communication protocol which is used in the call control for communication of images, audio, and video using an Internet Protocol (IP). 
     In the first exemplary embodiment, a case is described where the MFP  210  transmits a call to the MFP  220  for sending image data, and a response from the MFP  220  to the call indicates that the MFP  220  is in a non-receivable status. In this case, the MFP  210  requests the MFP  220  to notify the MFP  210  when the MFP  220  has shifted to a receivable status. Further, the MFP  210  secures a communication channel for sending the image data to the MFP  220  until a notification from the MFP  220  is received. 
       FIG. 3  illustrates a sending sequence of the image data from the MFP  210  to the MFP  220  in the first exemplary embodiment.  FIG. 3  illustrates an example where the MFP  210  transmits a call to the MFP  220  for sending the image data, but the MFP  220  is in the non-receivable status, therefore the MFP  210  requests the MFP  220  to notify the MFP  210  that the MFP  220  has shifted to the receivable status, and secures the communication channel. 
       FIGS. 4 and 5  are flowcharts illustrating a series of operations in the MFP  210 , when the image data is sent from the MFP  210  to the MFP  220 . The CPU  163  of the MFP  210  (MFP  100 ) controls the series of operations illustrated in these flowcharts based on respective programs stored in the program ROM  175 . 
     First, in step S 401 , the MFP  210  transmits a call to the MFP  220 . More specifically, the MFP  210  sends “INVITE” of SIP message to the MFP  220 , as illustrated in step S 301  of  FIG. 3 . 
     Next, in step S 402 , the MFP  210  determines whether the MFP  220  is in the receivable status. If the MFP  220  is determined as in the receivable status (YES in step S 402 ), the process proceeds to step S 413 . If the MFP  220  is determined as in the non-receivable status (NO in step S 402 ), the process proceeds to step S 403 . Determination in step S 402  is performed according to a response from the MFP  220  to the call from the MFP  210 . That is, when “486 Busy Here” of the SIP message is sent from the MFP  220 , as illustrated in step S 302  of  FIG. 3 , then the MFP  210  determines that the MFP  220  is currently in the non-receivable status. On the other hand, when “200 OK” of the SIP message is sent from the MFP  220 , the MFP  210  determines that the MFP  220  is currently in the receivable status. When “486 Busy Here” is sent from the MFP  220 , the MFP  210  sends “ACK” of the SIP message to the MFP  220 , as illustrated in step S 303  of  FIG. 3 . 
     Further, in step S 403 , the MFP  210  transmits “SUBSCRIBE” of the SIP message to the MFP  220  as illustrated in step S 304  in  FIG. 3 . By sending the “SUBSCRIBE”, the MFP  210  can request the MFP  220  to notify the MFP  210  when the MFP  220  has shifted to the receivable status. In an expires field of “SUBSCRIBE”, information indicating a time-out period set by the user using a method as described below is stored. If the MFP  220  that received “SUBSCRIBE” has shifted to the receivable status during a period since the MFP  220  received “SUBSCRIBE” until the time-out period which is indicated by the information stored in the expiration field has elapsed, the MFP  220  notifies the MFP  210  to that effect. 
     In step S 404 , the MFP  210  determines whether notification request made by sending “SUBSCRIBE” is accepted by the MFP  220  on a receiving side. More specifically, when “200 OK” is sent from the MFP  220 , as illustrated in step S 305  in  FIG. 3 , the MFP  210  determines that the notification request is accepted. On the other hand, if “200 OK” is not sent, or any SIP message other than “200 OK” is sent, the MFP  210  determines that the notification request is not accepted. 
     When the notification request is accepted by the receiving apparatus (YES in step S 404 ) as a result of determination in step S 404 , the process proceeds to step S 405 . If the notification request is not accepted (NO in step S 404 ), the process terminates without any operation. In step S 405 , the MFP  210  secures the communication channel for sending the image data from the MFP  210  to the MFP  220  when the MFP  220  has shifted to the receivable status. This is because, even though the MFP  210  requests the MFP  220  to notify that the MFP  220  has shifted to the receivable status to send the image data to the MFP  220 , the MFP  210  can not send the image data if the MFP  210  is in a non-transmittable status, when the MFP  220  has shifted to the receivable status. 
     In the first exemplary embodiment, to avoid the above described situation, the MFP  210  sends the notification request to the MFP  220 , and secures the communication channel for sending the image data to the MFP  220  on the basis that the notification request is accepted. In other words, the MFP  210  prohibits use of the communication channel for sending the image data to the MFP  220  for data communication with apparatuses other than the MFP  220 , and becomes ready for immediately sending the image data to the MFP  220  when the MFP  210  is notified that the MFP  220  has shifted to the receivable status. 
     Here, an example of securing the communication channel on the basis that the notification request from the MFP  210  is accepted by the MFP  220  (namely, on the basis that the MFP  210  is received “200 OK” in step S 305 ) is described, but other embodiments are available. For example, the MFP  210  may secure the communication channel based on that the MFP  210  sends “SUBSCRIBE” in step S 304 . 
     Further, the present exemplary embodiment describes an example of securing the communication channel after sending the notification request to the MFP  220  when it is determined that the MFP  220  is in the non-receivable status, but other aspects are available. For example, if the MFP  220  has a function to notify the sending apparatus that the MFP  220  has shifted to the receivable status when a call from the sending apparatus is transmitted, even if the sending apparatus does not send the notification request, the MFP  210  does not need to send the notification request. In this case, the MFP  210  may secure the communication channel on the basis that the MFP  210  determines that the MFP  220  is in the non-receivable status. 
     Further, if the MFP  210  has a plurality of communication channels and can respectively execute data communication with a plurality of MFPs in parallel, the MFP  210  has only to secure at least one communication channel among the plurality of communication channels. In this case, other communication channels except for the secured communication channel are permitted to be used for communication with apparatuses other than the MFP  220 . 
     Next, in step S 406 , the MFP  210  stores and manages information for identifying a destination (i.e., MFP  220 ) to which “SUBSCRIBE” is sent in the external memory  130 . Here, any information can be used for identifying the MFP  220  as long as the information can uniquely identify the MFP  220 , such as tag information of From Header of the SIP message and Call_ID. 
     Then, in step S 407 , the MFP  210  determines whether a predetermined time has elapsed since the MFP  210  secured the communication channel for sending the image data to the MFP  220 . The predetermined time is set in advance by the user using a method as described below. When the predetermined time has elapsed as a result of determination in step S 407  (YES in step S 407 ), the process proceeds to step S 411 , and if not elapsed (NO in step S 407 ), the process proceeds to step S 408 . 
     In step S 408 , the MFP  210  determines whether there is the notification from the MFP  220  that the MFP  220  has shifted to the receivable status. More specifically, when “NOTIFY” of the SIP message is sent from the MFP  220 , as illustrated in step S 306  in  FIG. 3 , the MFP  210  determines that there is the notification that the MFP  220  has shifted to the receivable status. If there is the notification from the MFP  220  (YES in step S 408 ), the MFP  210  sends “200 OK” in step S 307 , then the process proceeds to step S 409 . If there is no notification from the MFP  220  (NO in step S 408 ), the process returns to step S 407 . 
     When making a determination in step S 408 , the MFP  210  determines whether an MFP that has sent “NOTIFY” is the MFP (the MFP  220 ) that is indicated by the information managed in step S 406 . As a result of the determination, if the MFP that has sent “NOTIFY” is the MFP (the MFP  220 ) that is indicated by the information managed in step S 406 , the MFP  210  determines that there is the notification from the MFP  220 . On the other hand, if the MFP that has sent “NOTIFY is not the MFP (the MFP  220 ) that is indicated by the information managed in step S 406 , the MFP  210  determines that there is no notification from the MFP  220 , and the process returns to step S 407 . 
     In step S 409 , the MFP  210  again transmits the call for sending the image data to the MFP  220  similar to step S 401 . That is, as illustrated in  FIG. 3 , the MFP  210  sends “INVITE” to the MFP  220 , in step S 308 . Then, if “200 OK” is sent from the MFP  220  in step S 309 , the MFP  210  sends “ACK” to the MFP  220  in step S 310 . After that, in step S 410 , the process moves to a media session and the MFP  210  sends the image data to the MFP  220 . 
     In step S 402 , if the MFP  220  is determined as in the receivable status (YES in step S 402 ), the MFP  210  similarly sends the image data. In other words, the MFP  210  sends “ACK” to the MFP  220 , then in step S 413 , the process moves to the media session, and the MFP  210  sends the image data to the MFP  220 . In  FIG. 3 , upon completion of sending the image data, the MFP  210  sends “BYE” of the SIP message to the MFP  220  in step S 311 , and further receives “200 OK” sent from the MFP  220  in step S 312 . 
     In step S 411 , the MFP  210  releases the secured communication channel for sending the image data to the MFP  220 . In other wards, the MFP  210  opens the communication channel secured in step S 405 , so that the communication channel can be used for data communication with other MFPs except for the MFP  220 . Further, in step S 412  and in step S 313 , the MFP  210  transmits again “SUBSCRIBE” to the MFP  220  to cancel the notification request. In the expiration field of “SUBSCRIBE” which is sent here, information indicating that the time-out period is zero is stored. By sending the “SUBSCRIBE”, the MFP  210  can cancel the notification request to the MFP  220  which was made by sending “SUBSCRIBE” in step S 403  and in step S 304 . If “200 OK” is sent from the MFP  220  in step S 314  as a response to “SUBSCRIBE” sent by the MFP  210 , a series of operations terminates. As described above, the MFP  210  can be ready for reliably sending the image data when the MFP  220  has shifted to the receivable status. 
       FIG. 6  illustrates a transition of screens for allowing a user to set the above described time-out period and time during which the communication channel is secured (predetermined time). Each screen illustrated in  FIG. 6  is displayed on a liquid crystal display unit provided in the operation panel unit  120 . 
     First, in step S 601 , if the user presses a user mode key provided in the operation panel unit  120 , the process proceeds to step S 602 , and the operation panel unit  120  displays a user mode screen. When a “sending/receiving specification setting” button is pressed on the screen, the process proceeds to step S 603 , and the operation panel unit  120  displays a sending/receiving specification setting screen. Further, when a “communication reservation setting” button is pressed on the screen, the process proceeds to step S 604 , and the operation panel unit  120  displays a communication reservation setting screen. 
     On the communication reservation setting screen, the user can individually set a time-out period to be stored in the expiration field of “SUBSCRIBE” which is sent in step S 403  of  FIG. 4  and a communication channel securing period used for a determination in step S 407 . Here, if the user sets, for example, a SUBSCRIBE time-out period at 10 minutes, and the communication channel securing period at 0 minutes, the MFP  210  does not secure the communication channel, even though the MFP  210  requests the receiving apparatus that is in the non-receivable status to notify when the receiving apparatus has shifted to the receivable status. In other words, if the MFP  210  is requested to start data communication with another apparatus before notification from the receiving apparatus that the receiving apparatus has shifted to the receivable status, the MFP  210  executes preferentially data communication with the other apparatus. In the screens illustrated in  FIG. 6 , the SUBSCRIBE time-out period and the communication channel securing period are designed to be individually set, but they may be collectively set as one setting. That is, either one of the SUBSCRIBE time-out period and the communication channel securing period is set, and the same period may be automatically set to the one that is not set in the screens. In this case, time and effort for setting that the user takes can be saved. In accordance with the first exemplary embodiment, a communication channel for sending image data may be secured when a receiving apparatus is in a non-receivable status, so that the image data can be sent to the receiving apparatus when the receiving apparatus has shifted to a receivable status. 
     In a second exemplary embodiment of the present invention, similar to the first exemplary embodiment, a case where the MFP  220  is in a non-receivable status when the MFP  210  transmits a call to the MFP  220  for sending image data will be described below. An example where the communication channel is secured at the MFP  210  side is described in the first exemplary embodiment, but in the second exemplary embodiment, an example where the communication channel is secured at the MFP  220  side will be described. More specifically, in the second exemplary embodiment, the MFP  220  secures the communication channel for receiving the image data from the MFP  210  during a period after notifying the MFP  210  that the MFP  220  has shifted to the receivable status until the MFP  210  receives again the call from the MFP  210  for sending the image data. 
       FIG. 7  illustrates a sending sequence of the image data from the MFP  210  to the MFP  220  according to the second exemplary embodiment.  FIG. 7  illustrates an example where the MFP  220  which is requested from the MFP  210  to notify when the MFP  220  has shifted to the receivable status secures the communication channel for receiving the image data from the MFP  210  after notifying the MFP  210  that the MFP  220  has shifted to the receivable status.  FIGS. 8 and 9  are flowcharts illustrating a series of operations in the MFP  220 , when the image data is sent from the MFP  210  to the MFP  220 . The CPU  163  of the MFP  220  (the MFP  100 ) controls the series operations illustrated in these flowcharts based on respective programs stored in a program ROM  175 . 
     First, in step S 801 , the MFP  220  receives a call from the MFP  210 . More specifically, the MFP  220  receives “INVITE” sent from the MFP  210 , as illustrated in step S 701  of  FIG. 7 . Next, in step S 802 , the MFP  220  determines whether it is in the receivable status. If the MFP  220  is in the receivable status (YES in step S 802 ), the MFP  220  sends “200 OK”, and the process proceeds to step S 814 . Alternatively, if the MFP  220  is determined as in the non-receivable status (NO in step S 802 ), the process proceeds to step S 803 , then the MFP  220  sends “486 Busy Here” in step S 702  in  FIG. 7 . Further, the MFP  220  receives “ACK” sent from the MFP  210  in step S 703 . Determination in step S 802  is performed based on whether the communication channel provided by the MFP  220  has been already used for data communication with an MFP other than MFP  210 . That is, if the communication channel is being used for data communication with the other MFP, it is determined that the MFP  220  is currently in the non-receivable status, because the MFP  220  can not be used for data communication with the MFP  210 . On the other hand, when the communication channel (at least one of channels if the MFP  220  has a plurality of communication channels) is not being used, it is determined that the MFP  220  is currently in the receivable status. 
     In step S 804 , the MFP  220  determines whether “SUBSCRIBE” is received. If “SUBSCRIBE” is sent from the MFP  210  (YES in step S 804 ), as illustrated in step S 704  of  FIG. 7 , the MFP  220  sends “200 OK” to the MFP  210  in step S 705 , then the process proceeds to step S 805 . When the MFP  220  has not received “SUBSCRIBE” (NO in step S 804 ), the process terminates as it is. 
     In the expiration field of “SUBSCRIBE”, the information about the SUBSCRIBE time-out period set by the user on the communication reservation setting screen displayed in step S 604  of  FIG. 6  is stored. In step S 805 , the MFP  220  determines whether the time-out period indicated by the information that is stored in the expiration field has elapsed since the MFP  220  received “SUBSCRIBE”. If the time-out period has not elapsed as a result of determination in step S 805  (NO in step S 805 ), the process proceeds to step S 806 . On the other hand, if the time-out period has elapsed (YES in step S 805 ), the process terminates as it is. 
     In step S 806 , the MFP  220  determines whether the MFP  220  is in the receivable status, similar to step S 802 . If it is determined that the MFP  220  is in the receivable status (YES in step S 806 ), the process proceeds to step S 807 , and if not (NO in step S 806 ), the process returns to step S 805 . In step S 807 , the MFP  220  secures the communication channel to prepare for receiving the image data from the MFP  210 . This is because even though the MFP  220  notified the MFP  210  that it has shifted to the receivable status, the MFP  220  cannot receive the image data if the MFP  220  has shifted again to the non-receivable status when the call is again transmitted from the MFP  210 . 
     In order to avoid the above described situation, in the second exemplary embodiment, the MFP  220  receives a notification request from the MFP  210 , the MFP  220  secures the communication channel for receiving the image data from the MFP  210  on the basis that the MFP  220  has shifted to the receivable status. That is, the MFP  220  prohibits the use of the communication channel for receiving the image data from the MFP  210  for data communication with apparatuses other than the MFP  210 , and becomes ready for immediately receiving the image data from the MFP  210 , when the call is transmitted again from the MFP  210 . 
     Here, the present embodiment describes an example where the MFP  220  secures the communication channel on the basis that the MFP  220  has shifted to the receivable status, but other exemplary embodiments are also available. For example, the MFP  220  may secure the communication channel on the basis that the MFP  220  sends “NOTIFY” to the MFP  210  in step S 808 . 
     Further, if the MFP  220  is in the non-receivable status when receiving the call from the sending apparatus, the MFP  220  may automatically notify the sending apparatus, which transmits the call, that the MFP  220  has shifted to the receivable status, even when “SUBSCRIBE” is not sent from the sending apparatus. In this case, if “SUBSCRIBE” is not sent from the sending apparatus, the MFP  220  secures the communication channel on the basis that it has shifted to the receivable status. 
     Further, if the MFP  220  has a plurality of communication channels and can respectively execute data communication with a plurality of MFPs in parallel, the MFP  220  has only to secure at least one communication channel among the plurality of communication channels. In this case, other communication channels except for the secured communication channel are permitted to be used for communication with apparatuses other than the MFP  210 . 
     In step S 808 , the MFP  220  sends “NOTIFY” to the MFP  210  as illustrated in step S 706  in  FIG. 7 . That is, the MFP  220  notifies the MFP  210  that the MFP  220  has shifted to the receivable status. Then, the MFP  220  receives “200 OK” sent from the MFP  210  in step S 707 . 
     In step S 809 , the MFP  220  stores and manages information for identifying a destination (i.e., the MFP  210 ) to which the MFP  220  send “NOTIFY” in the external memory  130 . Here, any information can be used for identifying the MFP  210  as long as the information can uniquely identify the MFP  210 , such as tag information of From Header of the SIP message and Call_ID. 
     Then in step S 810 , the MFP  220  determines whether a predetermined time has elapsed since the MFP  220  secured the communication channel necessary for receiving the image data from the MFP  210 . The predetermined time is based on the communication channel securing period which is set by the user on the communication reservation setting screen displayed in step S 604  of  FIG. 6 . If the predetermined time has elapsed (YES in step S 810 ) as a result of determination in step S 810 , the process proceeds to step S 813 , and if not (NO in step S 810 ), the process proceeds to step S 811 . 
     In step S 811 , the MFP  220  determines whether the MFP  220  has received the call again from the MFP  210 . More specifically, if “INVITE” is sent from the MFP  210 , as illustrated in step S 708  of  FIG. 7 , the MFP  220  determines to have received the call from the MFP  210 . 
     If the MFP  220  has received the call from the MFP  210  (YES in step S 811 ) as a result of determination in step S 811 , then the MFP  220  sends “200 OK” to the MFP  210  in step S 709  and receives “ACK” sent from the MFP  210  in step S 710 . On the other hand, if the MFP  220  has not received the call from the MFP  210  (NO in step S 811 ), the process returns to step S 810 . 
     When making a determination in step S 811 , the MFP  220  determines whether an MFP that has sent “INVITE” is the MFP (the MFP  210 ) that is indicated by the information managed in step S 809 . As a result of the determination, if the MFP that has sent “NOTIFY” is the MFP (the MFP  210 ) that is indicated by the information managed in step S 809 , the MFP  220  determines to have received the call from the MFP  210 . On the other hand, if the MFP that has sent “INVITE” is not the MFP (the MFP  210 ) that is indicated by the information managed in step S 809 , the MFP  220  determines to have not yet received the call from the MFP  210 . 
     In step S 812 , the process moves to the media session, and the MFP  220  receives the image data from the MFP  210 . Similarly, if the MFP  220  is determined as in the receivable status in step S 802  (YES in step S 802 ), the process moves to the media session, and the MFP  220  receives the image data from the MFP  210  in step S 814 . 
     In  FIG. 7 , upon receiving the image data, the MFP  220  receives “BYE” sent from the MFP  210  in step S 711 , then in step S 712 , the MFP  220  sends “200 OK” as a response to the MFP  210 . 
     In step S 813 , the MFP  220  releases the secured communication channel for receiving the image data from the MFP  210 . That is, the MFP  220  opens the communication channel secured in step S 807 , so that the communication channel can be used for data communication with other MFPs except for the MFP  210 . 
     Here, the MFP  220  manages information indicating a sending source (the MFP  210 ) of the “SUBSCRIBE” on the basis that the MFP  220  has received “SUBSCRIBE” in step S 804 . Further, the MFP  220  erases the information on the basis that the MFP  220  has sent “NOTIFY” in step S 808 . However, the MFP  220  may erase the information by the following method instead of erasing the information on the basis that the MFP  220  has sent “NOTIFY”. 
     That is, the MFP  220  may erase the above described information on the basis that “SUBSCRIBE” in which information indicating that the time-out period in the expiration field is zero is stored is sent in step S 713  after the MFP  220  received the image data from the MFP  210 . In step S 714 , the MFP  220  sends “200 OK” to the MFP  210  on the basis that “SUBSCRIBE” is sent in step S 713 . As described above, the MFP  220  can be ready for reliably receiving the image data when receiving the call again from the MFP  210  after notifying the sending apparatus that the own apparatus has shifted to the receivable status. In accordance with the second exemplary embodiment, a communication channel necessary for receiving image data may be secured when a receiving apparatus has shifted to a receivable status, so that the image data can be received by the receiving apparatus. 
     A third exemplary embodiment of the present invention describes a case where the MFP  210  transmits a call to the MFP  220  for sending the image data and a response from the MFP  220  to the call indicates that the MFP  220  is in the non-receivable status similar to a first exemplary embodiment. Differences between the third exemplary embodiment and the first exemplary embodiment is that a new step S 1001  is added between step S 402  and step S 403  in the flowchart of  FIG. 4  which is described in the first exemplary embodiment. 
       FIG. 10  is a flowchart for illustrating a series of operations in the MFP  210  when the image data is sent from the MFP  210  to the MFP  220 , which corresponds to the flowchart illustrated in  FIG. 4 . According to the third exemplary embodiment, if the MFP  220  is determined as in the non-receivable status in step S 402  in  FIG. 4  (NO in step S 402 ), the process proceeds to step S 1001  in  FIG. 10  before proceeding to step S 403 . 
     In step S 1001 , the MFP  210  determines whether to send “SUBSCRIBE” to the MFP  220 . More specifically, the MFP  210  determines whether to send “SUBSCRIBE” to the MFP  220  based on information indicating the MFP to which the MFP  210  should send “SUBSCRIBE” that the user sets beforehand using a method as described below. If it is determined that the MFP  210  should send “SUBSCRIBE” (YES in step S 1001 ), the process proceeds to step S 403 , then in step S 304  in  FIG. 3 , the MFP  210  sends “SUBSCRIBE” to the MFP  220 . On the other hand, if it is not determined that the MFP  210  should send “SUBSCRIBE” (NO in step S 1001 ), the process terminates as it is. 
       FIG. 11  illustrates a transition of screens for registering a new destination in an address book table which is stored and managed in the external memory unit  130 . Each screen illustrated in  FIG. 11  is displayed on the liquid crystal display unit provided in the operation panel unit  120 . 
     First, in step S 1101 , if a user presses the user mode key provided in the operation panel unit  120 , the process proceeds to step S 1102 , and the operation panel unit  120  displays the user mode screen. If an “address book specification setting” button is pressed on the screen, the process proceeds to step S 1103 , and the operation panel unit  120  displays an address book specification setting screen. Further, if a “register new destination” button is pressed on the screen, the process proceeds to the step S 1104 , and the operation panel unit  120  displays a new destination registration screen. On the new destination registration screen, the user inputs destination information used for specifying a sending destination of the image data and information used for determination in step S 1001  of  FIG. 10 . That is, the user inputs a name and e-mail address and/or telephone number of the destination of the image data on the new destination registration screen, and selects ON/OFF of a communication reservation flag. When the user presses a “register” button, then in step S 1105 , the inputted information is registered in the address book. 
       FIG. 12  illustrates an address book table for managing the information input via the new destination registration screen as illustrated in  FIG. 11 . As illustrated in  FIG. 12 , information about destination numbers, destination names, addresses/telephone numbers, and information indicating ON/OFF of the communication reservation flag are managed in the address book table. The communication reservation flag is information indicating whether a notification that a destination of call is in the receivable status, is requested when it has shifted to the receivable status if “486 Busy Here” is sent from the destination of call. In other words, if it is determined that the MFP  220  is in the non-receivable status in step S 402  in  FIG. 4 , the MFP  210  refers to the address book table as illustrated in  FIG. 12  and determine that the MFP  210  sends “SUBSCRIBE” when the communication reservation flag of the MFP  220  is ON. In this case, when the destination of call is not registered in the address book table, the MFP  210  is set to determine that “SUBSCRIBE” is not to be sent. However, the MFP  210  may be set to determine that “SUBSCRIBE” is to be sent. 
     As described above, when the receiving apparatus is in the non-receivable status, the sending apparatus can determine whether to request the receiving apparatus to notify the sending apparatus of receivable status based on the information previously specified by the user. Consequently, if the receiving apparatus is in the non-receivable status, the present exemplary embodiment can prevent the sending apparatus from constantly sending “SUBSCRIBE”, and constantly securing the communication channel for sending the image data. In other words, the present exemplary embodiment can prevent a problem that the communication channel is secured to send the image data of low priority which cannot be executed because of the non-receivable status, so that other data communication of high priority cannot be executed. 
     A fourth exemplary embodiment of the present invention describes a case where the MFP  220  is in a non-receivable status when the MFP  210  transmits a call to the MFP  220  for sending image data similar to the first exemplary embodiment. In the first exemplary embodiment, the MFP  210  secures a communication channel, but in the fourth exemplary embodiment, the MFP  220  secures the communication channel. Differences between the fourth exemplary embodiment and the second exemplary embodiment is that a new step S 1301  is added between step S 804  and step S 805  in the flowchart of  FIG. 8  which is described in the second exemplary embodiment. 
       FIG. 13  is a flowchart for illustrating a series of operations in the MFP  220  when sending the image data from the MFP  210  to the MFP  220 , which corresponds to the flowchart as illustrated in  FIG. 8 . According to the fourth exemplary embodiment, in step S 804  of  FIG. 8 , if “SUBSCRIBE” is sent from the MFP  210  (YES in step S 804 ), the process proceeds to step S 1301  in  FIG. 13  before proceeding to step S 805 . 
     In step S 1301 , the MFP  220  determines whether to accept the request from the MFP  210  to notify the MFP  210  when the MFP  220  has shifted to the receivable status. More specifically, the MFP  220  determines based on the communication reservation flag which is set via the new destination registration screen illustrated in  FIG. 11  and managed by the address book table illustrated in  FIG. 12 . When “SUBSCRIBE” is sent from the MFP  210 , the MFP  220  refers to the address book table and accepts the notification request from the MFP  210  if the communication reservation flag of the MFP  210  is ON, then in step S 705 , the MFP  220  sends “200 OK”. Then, the process proceeds to step S 805 . On the other hand, if the communication reservation flag of the MFP  210  is OFF, the MFP  220  terminates the process as it is without sending “200 OK”. In this case, when a sending destination of “SUBSCRIBE” is not registered in the address book table, the notification request is not accepted. However, the notification request may be accepted. 
     As described above, when the receiving apparatus is requested from the sending apparatus to notify of shifting to the receivable status, the receiving apparatus can determine whether to accept the notification request based on the information previously specified by the user. Consequently, if the receiving apparatus is requested to notify the sending apparatus that the receiving apparatus has shifted to the receivable status, the present exemplary embodiment can prevent the receiving apparatus from constantly accepting the request notifying of shifting to the receivable status, and securing the communication channel. In other words, the present exemplary embodiment can prevent a problem that the communication channel is secured to receive the image data of low priority which the sending apparatus intends to receive, so that other data communication of high priority cannot be received. 
     Configurations in the first through fourth exemplary embodiments as described above may be individually provided, or may be provided in combination with one another. For example, one communication apparatus may be configured with a sending apparatus described in the first or the third exemplary embodiment and a receiving apparatus described in the second or the fourth exemplary embodiment. Further, the SUBSCRIBE time-out period and the communication channel securing period that can be set on the communication reservation setting screen as illustrated in  FIG. 6  may be set for each destination on the new destination registration screen as illustrated in  FIG. 11 . Consequently, a communication reservation method can be individually set for each destination and usability can be improved. 
     The above described exemplary embodiments of the present invention include, for example, a system, an apparatus, a method, a program and a storage medium (recording medium). More specifically, the exemplary embodiments of the present invention may be applied to a system including a plurality of devices and an apparatus including a single device. 
     The present invention includes a case where a program of software that achieves functions of the above described exemplary embodiments (a program corresponding to the flowcharts illustrated in drawings in the exemplary embodiments) is directly or remotely supplied to a system or an apparatus, and a computer included in the system or the apparatus reads out and executes the supplied program code to achieve the functions of the exemplary embodiments. 
     Accordingly, the program code itself which is installed in the computer to achieve the functions and processes of the exemplary embodiments of the present invention by the computer constitutes the above-described embodiments. In other words, the computer program itself for achieving the functions and processes of the exemplary embodiments of the present invention constitutes the present invention. In this case, the program can be in any form, such as object code, a program executed by an interpreter, and script data supplied to an operating system (OS) so long as they have a function of a program. 
     A recording medium for supplying a program includes a floppy disk, a hard disk, an optical disc, a magneto-optical disk (MO), a compact disc read-only memory (CD-ROM), a compact disc-recordable (CD-R), a compact disc-rewritable (CD-RW), a magnetic tape, a non-volatile memory card, a read-only memory (ROM), a digital versatile disc (DVD) (a DVD-read only memory (DVD-ROM), a DVD-recordable (DVD-R)). 
     As a method for supplying a program, the program can be downloaded from an Internet website to a recording medium such as a hard disk using a browser of a client computer. That is, the client computer is connected to a website, and the computer program of the exemplary embodiments of the present invention or a compressed file including an automated installation function can be downloaded from the website. Further, the present invention can be implemented by dividing a program code that constitutes the program of the exemplary embodiments of the present invention into a plurality of files, and downloading each file from different websites. In other words, a World Wide Web (WWW) server which allows a plurality of users to download a program file for achieving the functions and processes of the exemplary embodiments of the present invention on a computer also constitutes the present invention. 
     Furthermore, the program of the exemplary embodiments of the present invention can be encrypted, stored in a computer-readable storage medium, such as a CD-ROM, and distributed to users. In this case, a user who satisfies a predetermined condition can download decryption key information from a website via the Internet. Then, the user can execute the encrypted program by using the key information, and install the program on the computer to implement the present invention. 
     Further, a computer reads out and executes a program to implement the functions of the above described exemplary embodiments. Alternatively, an operating system (OS) or the like running on the computer can perform a part or whole of the actual processing based on an instruction of the program and implement the functions of the above described exemplary embodiments. 
     Further, the functions of the above described exemplary embodiments can also be implemented when the program read out from a recording medium is written in a memory provided in a function expansion board inserted into a computer or a function expansion unit connected to the computer, and a CPU of the function expansion board or the function expansion unit execute a part or whole of the actual processing based on the instruction of the program. 
     While the present invention has been described with reference to the exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications, equivalent structures, and functions. 
     This application claims priority from Japanese Patent Application No. 2008-067732 filed Mar. 17, 2008, which is hereby incorporated by reference herein in its entirety.