Patent Publication Number: US-2006020661-A1

Title: Apparatus and method for displaying content

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims priority from Korean Patent Application Nos. 10-2004-0058074 and 10-2004-0063882 filed on filed on Jul. 24, 2004 and Aug. 13, 2004, respectively, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference in their entireties.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      Apparatuses and methods consistent with the present invention relate to a service for displaying content, and more particularly, to efficiently providing content by supplying a plurality of display apparatuses and a single server which are connected through a network and perform predetermined message communication, and allowing the server to remotely control and monitor the display apparatuses.  
      2. Description of the Related Art  
       FIG. 1  is a schematic diagram of a conventional system  100  for providing a service of displaying content.  
      The conventional system  100  includes display apparatuses  110 ,  130 , and  150  and servers  120 ,  140 , and  160 , which are connected to the display apparatuses  110 ,  130 , and  150 , respectively, to provide content. Content includes multimedia data such as music, images, motion pictures, and data having diverse text formats.  
      Various kinds of software programs are installed in or independent hardware containing these programs is mounted to each of the servers  120 ,  140 , and  160  to convert content stored therein into a format suitable for the corresponding display apparatuses  110 ,  130 , and  150  to output. Accordingly, the output format of the content selected by a server manager is converted using these software program, and the converted content is output by a display apparatus.  
      A display apparatus may include a function that allows a user to select content, receive the selected content from a server, and output the content. In this case, the display apparatus serves as a client.  
       FIG. 2  illustrates a method of providing a content display service between such a client and server.  
      In operation S 210 , a client connects with a server using address and port information of the server while the server is operating. In operation S 220 , the client requests a service from the server. In operation S 230 , the server retrieves the requested service and provides the service to the client.  
      According to a conventional system like that shown in  FIG. 1 , a separate server having a format conversion function is needed for each display apparatus and a server manager needs to select content to be output through the display apparatus. In addition, when the client-server structure shown in  FIG. 2  is used, the server has difficulty in controlling a client display apparatus and monitoring changes in the physical state of the display apparatus. The server may control the display apparatus using Universal Plug-and-Play (UPnP) standard. In UPnP, a remote control and monitoring service is implemented based on the HyperText Markup Language (HTML). Accordingly, an HTML browser and parser are needed to analyze a message and hardware or software having HyperText Transfer Protocol (HTTP) functionality are needed to perform the UPnP protocol. However, messages or remote control commands are valid only when it defined in the UPnP protocol. As a result, there are a lot of restrictions on both the remote control commands and the method of monitoring the changes in state of the display apparatuses. Moreover, even when just a simple remote control command is performed, an HTTP server and HTML parser software are needed.  
      Therefore, to overcome these conventional problems, an apparatus and method for displaying content, which involves a server efficiently providing content to display apparatuses and remotely controlling and monitoring the display apparatuses, are desired.  
     SUMMARY OF THE INVENTION  
      The present invention provides an apparatus and method for displaying contents, by which contents are automatically provided to a plurality of display apparatuses having a message communication function using a single server.  
      The present invention also provides an apparatus and method for displaying contents, by which a plurality of display apparatuses having a message communication function are remotely controlled and the change in a physical state of each display apparatus is monitored using a single server.  
      According to an aspect of the present invention, there is provided an apparatus for displaying contents, including a device interface module automatically sensing a server connected to the display apparatus through a network and receiving content pushed according to a predetermined schedule and a control command from the server, a control and monitoring module receiving the control command from the device interface module, performing state control corresponding to the control command, and sensing a state change, a content processing module converting the content received from the device interface module into a format suitable for display, a display module outputting the content converted by the content processing module, and a device agent module analyzing information received through the device interface module and performing an operation according to the analyzed information.  
      According to another aspect of the present invention, there is provided a server apparatus including a server interface module automatically sensing a display apparatus connected to the server through a network, extracting information on the display apparatus, and transmitting content and a control command for controlling the display apparatus to the display apparatus, a storage module storing the content and schedule information on a schedule in which the content is pushed to the display apparatus, a scheduling module managing the schedule information and pushing the content according to the schedule information, a user interface module providing a user interface allowing a user to input the schedule information and the control command for the display apparatus, and a server agent module analyzing information provided through the server interface module, performing an operation according to the analyzed information, and monitoring state information received from the display apparatus.  
      According to still another aspect of the present invention, there is provided a method of displaying contents, including automatically sensing a server connected through a network and receiving one of content pushed according to a predetermined schedule and a control command from the server, converting the received content into a format suitable for display, outputting the converted content, performing state control according to the received control command, and transmitting state information comprising one of a result of performing the state control and information on an output state of the content.  
      According to a further aspect of the present invention, there is provided a method of displaying contents, including receiving from a user one of schedule information on a schedule in which content is pushed to a display apparatus and a control command for the display apparatus, managing the schedule information, pushing the content to the display apparatus according to the schedule information, transmitting the control command to the display apparatus, and monitoring state information received from the display apparatus, the state information comprising one of a result of executing the control command and information on an output state of the content. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other aspects of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:  
       FIG. 1  is a schematic diagram of a conventional system for providing a service of displaying content;  
       FIG. 2  illustrates a conventional method of providing a service between a client and a server;  
       FIG. 3  is a schematic diagram of a system for providing a service of displaying content according to an exemplary embodiment of the present invention;  
       FIG. 4  illustrates a display apparatus and a server for providing a service of displaying content according to an exemplary embodiment of the present invention;  
       FIG. 5  is a schematic flowchart of a procedure performed by a display apparatus to display content according to an exemplary embodiment of the present invention;  
       FIG. 6  is a schematic flowchart of a procedure performed by a server to display content according to an exemplary embodiment of the present invention;  
       FIG. 7  illustrates a service registration procedure according to an exemplary embodiment of the present invention;  
       FIG. 8  illustrates a procedure for performing a pull mode of service according to an exemplary embodiment of the present invention;  
       FIG. 9  is illustrates a procedure for performing a push mode of service according to an exemplary embodiment of the present invention;  
       FIG. 10  illustrates a procedure for performing a remote control service according to an exemplary embodiment of the present invention;  
       FIGS. 11A and 11B  illustrate procedures for finishing a service according to an exemplary embodiment of the present invention; and  
       FIG. 12  is a block diagram of a remote control and monitoring system according to an exemplary embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION  
      The present invention and methods of accomplishing the same may be understood more readily by reference to the following detailed description of exemplary embodiments and the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the invention to those skilled in the art, and the present invention will only be defined by the appended claims. Like reference numerals refer to like elements throughout the specification.  
      The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.  
      The present invention is described hereinafter with reference to flowchart illustrations of methods according to exemplary embodiments of the invention. It will be understood that each block of the flowchart illustrations, and combinations of blocks in the flowchart illustrations, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to create means for implementing the functions specified in the flowchart block or blocks.  
      These computer program instructions may also be stored in a computer usable or computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions implement the function specified in the flowchart block or blocks.  
      The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process for implementing the functions specified in the flowchart block or blocks.  
       FIG. 3  is a schematic diagram of a system  300  for providing a service of displaying content according to an exemplary embodiment of the present invention. The system  300  includes a server  310 , a plurality of display apparatuses  330 ,  340 , and  350 , which receive content from the server  310  and output it, and a transmission medium  320 , which connects the server  310  with the plurality of display apparatuses  330 ,  340 , and  350 . Each of the display apparatuses  330 ,  340 , and  350  may be a television, a monitor, or a large display apparatus like an electric signboard.  
      Unlike a conventional system, the server  310  provides content stored therein to a particular display apparatus  330 ,  340 , or  350  according to a predetermined schedule, and the display apparatus  330 ,  340 , or  350  receive the content and convert the format of the content into an output format that it supports. Accordingly, the display apparatuses  330 ,  340 , and  350  are equipped with hardware or software for converting the diverse data formats of the content.  
      In addition, the server  310  can remotely control the display apparatuses  330 ,  340 , and  350  and monitor state changes occurring in the display apparatuses  330 ,  340 , and  350 .  
      Information is transferred between the server  310  and each of the display apparatuses  330 ,  340 , and  350  using a message communication method, which will be described later.  
       FIG. 4  illustrates a display device  410  and a server  450  for providing a service for displaying content according to an exemplary embodiment of the present invention.  
      The display device  410  includes a display module  415 , a device agent module  420 , a device interface module  425 , a content processing module  430 , and a control and monitoring module  435 .  
      The display module  415  displays content received from the server, provides a user with a means to both request particular content stored in the server  450 , and control the display apparatus  410 . This means display device  410  may be provided as an independent module such as a device user interface module.  
      The device interface module  425  automatically senses another display apparatus and the server  450 , which are connected thereto through a network, and extracts information on the sensed display apparatus and the server  450 , and performs message communication with the sensed display apparatus or the server  450 .  
      The content processing module  430  converts content received from the server  450  to a suitable format for the display device  410  and transmits the converted content to the display module  415 .  
      When the display device  410  receives a control command from the server, the control and monitoring module  435  performs an operation corresponding to the message. In addition, the control and monitoring module  435  senses state changes in the display apparatus  410 .  
      The device agent module  420  analyzes messages received through the device interface module  425  and performs operations corresponding to the messages. In addition, the device agent module  420  controls the display module  415 , the control and monitoring module  435 , and the content processing module  430 .  
      The server  450  includes a server interface module  455 , a scheduling module  460 , a server agent module  465 , a storage module  470 , and a user interface module  475 .  
      The server interface module  455  automatically senses a plurality of display apparatuses connected therewith through a network, extracts information on each sensed display apparatus, and performs message communication with the plurality of display apparatuses.  
      The storage module  470  stores content and schedule information, i.e., information about a schedule for automatically transmitting content (i.e., pushing content) to each of the display apparatuses. The content includes sound files such as music, image files such as photos, video files such as motion pictures, and text files having diverse formats.  
      The user interface module  475  allows a server manager to search for content stored in the storage module  470  using a keyword or an index, and it allows the server manager to register a schedule indicating content to be transmitted to display apparatuses at a specific times. In addition, the user interface module  475  allows the server manager to input a remote control command so that the server manager can remotely control the plurality of display apparatuses, and it shows information on state changes in the plurality of display apparatuses.  
      The scheduling module  460  manages the schedule information and transmits particular content to a designated display apparatus at a particular time.  
      The server agent module  465  analyzes messages received through the server interface module  455  and performs operations according to the messages. In addition, the server agent module  465  controls the user interface module  475 , the scheduling module  460 , and the storage module  470 .  
      The term “module”, as used herein, means, but is not limited to, a software or hardware component, such as a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), which performs certain tasks. A module may advantageously be configured to reside on an addressable storage medium and to execute on one or more processors. Thus, a module may include, by way of example, components such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functionality provided for in the components and modules may be combined into fewer components and modules or further separated into additional components and modules. In addition, the components and modules may be implemented such that they execute one or more computers in a communication system.  
      Hereinafter, operations between the modules will be described in detail. For clarity, a procedure for displaying content and a procedure for remote control and monitoring will be described separately.  
      Content Display Service  
      Mutual Recognition Between a Display Apparatus and a Server  
      The server  450  and the display device  410  are connected to a single network through the server interface module  455  and the device interface module  425 , respectively. Here, the server  450  may be connected with a plurality of display apparatuses, but for clarity, the description will be set forth with respect to a single display apparatus, and it is assumed that the structure of other display apparatuses is the same as that of the display device  410  show in  FIG. 4 .  
      The server interface module  455  and the device interface module  425  senses whether a display apparatus or a server connected thereto has been supplied with power to operate. For example, in the server  450 , the server interface module  455  senses the display device  410  and transmits the sensing result to the server agent module  465 . Then, the server agent module  465  provides a server manager with information on the state of the display device  410  through the user interface module  475 . Accordingly, the server manager can check the states of display apparatuses at the server  450  site, without directly going to the site of each display apparatus to manually check them.  
      Scheduling  
      To display content on the display apparatus  410 , a server manager searches for the content stored in the storage module  470  by inputting a keyword and an index through the user interface module  475 . Next, the server manager inputs a time into the user interface module  475  when the searched content is to be displayed on the display device  410 .  
      Information on the searched content and schedule information display device  410  are managed by the scheduling module  460 . Accordingly, the scheduling module  460  transmits the schedule information to the server agent module  465  at the display time. Then, the server agent module  465  fetches the content from the storage module  470  and transmits it to the display device  410  through the server interface module  455 .  
      Outputting of Content  
      When the display device  410  receives data from the server  450  through the device interface module  425 , the device agent module  420  determines whether the received data is content for outputting or data for controlling the display apparatus  410 .  
      When it is determined that the received data is content for outputting, that is, when content is transmitted from the server  450  according to the operation of the scheduling module  460 , the device agent module  420  transmits the received data to the content processing module  430 .  
      The content processing module  430  converts the data received from the device agent module  420  into a format suitable for the display device  410  and drives an application program to output the converted content. The content output through the application program is provided to a user through the display module  415 .  
      Meanwhile, the user of the display device  410  may request particular content from the server  450  through the display module  415 . In this case, the display module  415  is provided with a function allowing the user to input content information. Here, the display device  410  may receive a content list (stored in advance in the storage module  470  after being received from the server  450 ) and provide this content list to the user through the display module  415  at the user&#39;s request for content. Alternatively, the display device  410  may request the content list from the server  450  only in response to a user&#39;s request for content.  
      Application Examples  
      Several representative application examples of the present invention will be described below.  
      Electronic Art Gallery  
      The server  450  converts works of art possessed by an art gallery into high-definition image data and stores them in the storage module  470 . The display device  410  is installed in an art gallery or a public space having a space for exhibition and connected to the server  450  through a network.  
      A server manager decides schedule information including the order in which images are displayed on the display device  410  and display related information through the user interface module  475  and registers the schedule information in the scheduling module  460 . The scheduling module  460  transmits the schedule information to the server agent module  465  at a designated time. The server agent module  465  fetches the image data from the storage module  470  based on the schedule information and transmits the image data to the display device  410  through the server interface module  455  so that a user can view the works of art.  
      Airport Information Service  
      The server  450  stores an airport guide, airline information, advertisements, entertainment video/audio content, and other information in the storage module  470 . The display device  410  is installed at a desired place within an airport and connected to the server  450  through a network.  
      The scheduling module  460  of the server  450  manages the order and content of information to be provided to the display apparatus  410 . The server transmits particular content to the display device  410  at a predetermined time. The display device  410  receives the content, converts it into an appropriate format, and displays it on a screen.  
      Information Presentation Service  
      The server  450  stores guide and presentation content in the storage module  470 . The display device  410  is installed at a desired place in a public space and is connected to the server  450  through a network.  
      The scheduling module  460  of the server  450  manages the order and composition of the guide and presentation content to be provided to the display apparatus  410 . The server transmits particular content to the display device  410  at a predetermined time. The display device  410  receives the content, converts it into an appropriate format, and displays it on a screen.  
      Remote Control and Monitoring  
      The server  450  can remotely control the display device  410  according to the state of the display apparatus  410 . For remote control operation, the server  450  and the display device  410  use a remote control message set and the display device  410  includes the control and monitoring module  435  for such purposes.  
      For example, when a server manager wants to turn on or off the power of the display device  410  or control an output state such as the volume or contrast, the server manager inputs a control command through the user interface module  475 . Here, the user interface module  475  provides the server manager with a user interface for controlling the display apparatus  410 .  
      In addition, the server  450  can remotely command navigation motions such as stop, pause, forward, and backward with respect to content output by the display apparatus  410 .  
      At the same time, the control and monitoring module  435  of the display device  410  senses state changes and transmits information on the sensed state change to the device agent module  420 . The device agent module  420  transmits this information to the server  450  through the device interface module  425 . As a result, the server  450  can remotely monitor the state of the display apparatus  410 .  
      The detailed description of remote control and monitoring display device  410  will be set forth later.  
      Message communication is performed between the display device  410  and the server  450 , and this is described in detail below. For clarity, the display device  410  is referred to as a client  410  and is described with reference to  FIG. 4 . The server agent module  455  in the server  450  and the device agent module  420  in the client  410  perform operations of generating a packet and analyzing a received message in order to accomplish message communication.  
      A message communication protocol according to an exemplary embodiment of the present invention is largely divided into message communication for: registering a client as a service target in order to start a service (see  FIG. 7 ), initiating a pull mode of service of the server (see  FIG. 8 ), initiating a push mode service from the server to the client (see  FIG. 9 ), remote control operation performed by the server with respect to the client (see  FIG. 10 ), finishing a service between the server and the client (see  FIGS. 11A and 11B ).  
      An example of the pull mode of service is a server that provides music, and a client selects a desired music title from a list of music titles stored in the server and receives the desired music title from the server.  
      An example of the push mode of service, monitors supporting a network function are installed at many places in a waiting room of a bus terminal or a train station, and a server provides the monitors with departure and arrival times of trains or buses, announcements, movies, and music.  
       FIG. 5  is a schematic flowchart of a procedure performed by the display device  410  to display content, according to an exemplary embodiment of the present invention.  
      In operation S 510 , the device interface module  425  of the display device  410  automatically senses other display apparatuses and a server which are connected thereto through a network, extracts information about both the sensed display apparatuses and the sensed server, and receives content that is automatically transmitted, i.e., pushed by the sensed server according to a schedule predetermined by a server manager or a control command from the server. In operation S 520 , the content processing module  430  converts the content received from the server into an output format supported by the display apparatus  410 . In operation S 530 , the display module  415  displays the converted content.  
      In operation S 540 , the control command received by the device interface module  425  is executed by the control and monitoring module  435  to control the state of the display apparatus  410 . In operation S 550 , the display device  410  transmits state information of the display apparatus  410 , i.e., information on the result of executing the control command or information on an output state of the content, to the server. Consequently, the server can remotely control and monitor the display apparatus  410 .  
       FIG. 6  is a schematic flowchart of a procedure performed by the server  450  to display content, according to an exemplary embodiment of the present invention.  
      In operation S 610 , the server receives either schedule information from a server manager that indicates a schedule for pushing content to a display apparatus or a remote control command for the display apparatus through the user interface module  475 . In operation S 620 , the scheduling module  460  manages the schedule information input by the server manager. In operation S 630 , the server agent module  465  pushes particular content to the display apparatus at a specific time according to the schedule information. In operation  640 , the server agent module  465  transmits a control command to remotely control the display apparatus. The display apparatus transmits state information regarding the outputting of content or the result of executing the control command to the server  450  periodically or when an event occurs, and the server  450  monitors this state information in operation S 650 .  
       FIG. 7  illustrates a service registration procedure according to an exemplary embodiment of the present invention. In the service registration procedure, the client  410  sends information to the server to register itself and to use a service provided by the server  450 .  
      Here, a packet used for the service registration includes a media access control (MAC) address, a service type, a group name, and a client name.  
      The MAC address is a unique identification number allocated to a network card included in the device interface module  425  that is used as an identifier for the client  410 . In addition, the MAC address can also be used when the server turns on the power of the client  410  in remote control operation.  
      The service type is a unique identifier for identifying a service of a different server.  
      The group name is the name of a group including the client  410  and it is used to manage a plurality of clients in groups.  
      The client name is an alias of the client  410 , which is familiar to a user, and is used to identify the client  410 .  
      When the client  410  sends a service registration request to the server  450 , as shown in  FIG. 7 , the server agent module  465  checks the service type and the group name. If the service type is supported by the server  450  and the group name corresponds to a group managed by the server  450 , the server agent module  465  stores information about the client  410  that requested registration in the storage module  470 . Here, the server  450  may be set to manage the list of registered clients by groups and to provide a service to a particular group or to clients in all groups.  
       FIG. 8  illustrates a procedure for performing a pull mode of service according to an exemplary embodiment of the present invention. When the client  410  uses content selected from a content list provided by the server  450 , the pull mode of service is performed.  
      Packets used for the pull mode of service include: a content list request packet containing a service type, a group name, a client name, a media type, list sorting information, and list request information; a content list packet containing a service type, a server name, a media type, content list information, and server service network information; a content request containing a service type, a group name, a client name, and content information; and a content finish packet containing a service type, a group name, a client name, and a media type. Here, the media type indicates a type of media, such as movies, music, photos, or document files, corresponding to relevant content.  
      The list sorting information indicates parameter information such as a name, a date, a file size, or a genre by which content is sorted in a list.  
      The list request information indicates the number of lists per page and the position of a page.  
      The content list information indicates a list of content information, i.e., a content list for a particular media type.  
      The server service network information is information on a network connection through which the server  450  provides a service which may include an Internet Protocol (IP) address and a port number.  
      When a multicast type of service is required, the server service network information may further include an IP address and a port number for multicasting.  
      The content information is information about the content and it may include a file name, a file length, a creation date, a genre, a running time, and image thumbnails.  
      Referring to  FIG. 8 , in operation S 810 , the device agent module  420  of the client  410  requests a content list for particular media from the server  450  through the device interface module  425  (a pull mode of service). Here, the client  410  transmits a pull mode content list request packet to the server  450 .  
      The server agent module  465  checks whether the requested service type is supported by the server  450  and whether the client  410  is a member of an authorized group.  
      Thereafter, in operation S 820 , the server agent module  465  retrieves content corresponding to the particular media from the storage module  470 , creates a content list, and transmits this content list to the client  410  using a pull mode content list packet.  
      In operation S 830 , the client  410  selects desired content from the content list and requests this selected content from the server  450  using a pull mode content request packet.  
      In operation S 840 , the server  450  checks whether the requested service type is supported and whether the client  410  is an authorized client, and transmits the requested content. When the client  410  wants to stop the pull mode of service, the client  410  transmits a pull mode content finish packet to the server  450  in operation S 850 .  
       FIG. 9  is illustrates a procedure for performing a push mode of service according to an exemplary embodiment of the present invention. The push mode of service may be used when the server  450  provides content to the client  410  when directed by the scheduling module  460 .  
      Here, packets used for the push mode service include a push mode content list packet containing a service type, a server name, a media type, content list information, and server service network information; a push mode content request packet containing a service type, a group name, a client name, and content information; and a push mode content finish packet containing a service type, a server name, and a media type.  
      Referring to  FIG. 9 , in operation S 910 , the server  450  transmits a content list to the client  410  connected thereto (a push mode of service). Here, a push mode content list packet is used.  
      In operation S 920 , the client  410  requests the server  450  to transmit content from the content list according to a predetermined sequence by sending a push mode content request packet.  
      In operation S 930 , the server  450  checks whether the requested service type is supported and whether the client  410  is an authorized client and transmits the requested content.  
      Operations S 920  and S 930  are repeated until all content on the content list is sent to the client  410 .  
      In operation S 940 , the server  450  can stop the push mode of service by transmitting a push mode content finish packet to the client  410 .  
       FIG. 10  illustrates a procedure for performing a remote control service according to an exemplary embodiment of the present invention. The remove control service can be used when the server  450  remotely controls a video or audio mode of the client  410  and remotely monitors the state of the client  410 .  
      Packets used for the remote control service include: a remote control packet containing a service type, a server name, a remote control command, and a remote control command parameter; and a client state packet containing a service type, a server name, and client state information.  
      Here, the remote control command indicates a control executed by the server  450  with respect to the client  410 . For example, the remote control command may be: Power On/Off, Wake up LAN, Adjust Contrast, Adjust Tint, Adjust Brightness, Adjust Volume, Adjust Video Mode, or Adjust Audio Mode. The Wake up LAN is a process of multicasting MAC address information of a network card to a local LAN and turning on the power of a CPU connected to the network card.  
      The client state information is state information including volume, a video mode, an audio mode, contrast, tint, and brightness of the client  410 .  
      In the remote control service shown in  FIG. 10 , in operation S 1010  the server  450  transmits a remote control command to the client  410  using a remote control packet.  
      The device agent module  420  of the client  410  analyzes this packet to determine whether the packet is involved in the remote control service. When it is determined that the packet is involved in the remote control service, the device agent module  420  transmits the remote control command to the control and monitoring module  435 . The control and monitoring module  435  executes the remote control command and reports a changed state resulting from this execution to the device agent module  420 . In operation S 1020 , the device agent module  420  transmits this changed state to the server  450  through the device interface module  425  using a client state packet.  
       FIGS. 11A and 11B  illustrate procedures for finishing a service according to an exemplary embodiment of the present invention. A service finishing procedure may be performed when the client  410  or the server  450  inform each other of completion of the service. Packets used to finish service include: a client service finish packet containing an MAC address, a service type, a group name, and a client name; and a server service finish packet containing a service type, and a server name.  
      The procedure shown in  FIG. 11A  is performed when the client  410  finishes the service. Referring to  FIG. 11A , the client  410  transmits a “client service finish packet” to the server  450 .  
      The procedure shown in  FIG. 11B  is performed when the server  450  finishes the service. Referring to  FIG. 11B , the server  450  transmits a server service finish packet to the client  410 . Here, the server  450  transmits a service finish message to every client connected thereto.  
      In addition, a message for periodically checking whether the server  450  and the client  410  are connected to each other can be transmitted and received therebetween. By using this message, the server  450  and the client  410  can recognize abnormal stops in service. A packet used to check the connection between the server  450  and the client  410  has an MAC address, a service type, a group name, and a client name.  
      A system for displaying content according to an exemplary embodiment of the present invention allows a plurality of display apparatuses to receive content from a single server and to display that content, and it also allows the server to control the display apparatuses and monitor state changes occurring in the display apparatuses. In other words, according to the present invention, a display apparatus not only outputs content but also executes various functions by communicating with the server as described above.  
       FIG. 12  is a block diagram of a remote control and monitoring system according to an exemplary embodiment of the present invention.  
      For remote control and monitoring, a server  450  contains a user interface  1210 , a server remote control and monitoring module  1220  including a remote control module  1222  and a remote monitoring module  1224 , a message parser  1230 , and a network interface  1240 .  
      The user interface  1210  is produced by the user interface module  475  shown in  FIG. 4  to provide an interface allowing a server manager to control a display device  410  and to know state information of the display apparatus  410 .  
      The message parser  1230  generates a message for controlling the display device  410  and analyzes a message regarding state information received from the display apparatus  410 . The functions of the message parser  1230  can be performed by the server agent module  465  shown in  FIG. 4 .  
      The remote control module  1222  transmits control information received from the user interface  1210  to the message parser  1230 . The remote monitoring module  1224  transmits state information of the display apparatus  410 , which is analyzed by the message parser  1230 , to the user interface  1210 .  
      The remote control module  1222  and the remote monitoring module  1224  may be included in the server agent module  465  or the user interface module  475 .  
      The network interface  1240  of the server  450  can be provided by the server interface module  455  shown in  FIG. 4 .  
      The client control and monitoring module  1250  of the display device  410  includes a microcomputer interface module  1252 , a state information processing module  1254 , and a remote control module  1256 , a message parser  1260 , and a network interface  1270 .  
      The network interface  1270  of the display device  410  can be provided by the device interface module  425  shown in  FIG. 4 .  
      The message parser  1260  generates a message including state information of the display device  410  or event information, and analyzes control information received from the server  450 . The functions of the message parser  1260  may be performed by the device agent module  420  shown in  FIG. 4 .  
      The remote control module  1256  transmits the control information the microcomputer interface module  1252 . The state information processing module  1254  senses events or state changes occurring in the display device  410  display device  410  transmits to the message parser  1260 .  
      The microcomputer interface module  1252  controls the hardware elements of the display apparatus  410 . The microcomputer interface module  1252  receives control information from the remote control module  1256  and controls relevant hardware element(s) accordingly.  
      The remote control module  1256 , the state information processing module  1254 , and the microcomputer interface module  1252  may be included in the control and monitoring module  435  shown in  FIG. 4 .  
      The remote control and monitoring function performed with respect to the display device  410  will be separately described in the following in terms of: remote control of the display device  410  by a server manager, and monitoring of a state change in the display apparatus  410 .  
      Remote Control of the Display Apparatus  410  by a Server Manager  
      For example, when turning off the power of the display apparatus  410 , the server manager checks the power states of display apparatuses through the user interface  1210  provided by the user interface module  475 .  
      When the server manager requires the display device  410  to be turned off; the remote control module  1222  receives and transmits the selection of the server manager to the message parser  1230 . The message parser  1230  creates a message for remote control and transmits the message to the display device  410  through the network interface  1240  of the server  450 .  
      The display device  410  receives the message through the network interface  1270 . The message parser  1260  analyzes the received message and transmits the analyzed information to the remote control module  1256 . Since the operation of turning on or off the power corresponds to a control over hardware elements, the remote control module  1256  drives the microcomputer interface module  1252  to turn off the power of the display apparatus  410 .  
      Through such operations the volume, contrast, brightness, monitor input, and other attributes of the display apparatuses can be adjusted.  
      Monitoring of a State Change in the Display Apparatus  410   
      State changes in the display device  410  include state changes resulting from remote control of the display device  410  and state changes display device  410  when independent of control by the server  450 . When a state change results from remote control of the display apparatus  410 , e.g., when the power state changes due to a power on/off from the server  450 , the state information processing module  1254  senses the changed state and transmits it to the message parser  1260 . The message parser  1260  creates a message indicating state information and transmits the message to the server  450  through the network interface  1270 .  
      The server  450  receives the message through the network interface  1240 . The message parser  1230  analyzes the received message and transmits analyzed information to the remote monitoring module  1220 . The remote monitoring module  1220  provides information on the state change to a server manager through the user interface  1210 .  
      When a state change occurs in the display device  410  when independent of control by the server  450 , the server  450  may periodically receive state information from all display apparatuses connected thereto via a network. The state information may include a list of connected display apparatuses, a network connection state of each display apparatus, and a current service status of each display apparatus. In addition, the display device  410  screen can be displayed on the server  450 . Furthermore, the server  450  may set the display device  410  to automatically operate to cope with a major event occurring in the display apparatus  410 .  
      In conclusion, those skilled in the art will appreciate that many variations and modifications can be made to the exemplary embodiments without substantially departing from the principles of the present invention. Therefore, the disclosed exemplary embodiments of the invention are used in a generic and descriptive sense only and not for purposes of limitation.  
      An apparatus and method for displaying content according to the present invention may provide the following advantages.  
      First, content is automatically provided by a server to a plurality of display apparatuses having message communication functionality that can be controlled by predetermined schedule information. Accordingly, content can be displayed without user management.  
      Second, the plurality of display apparatuses can be remotely controlled and changes in the physical state of each display apparatus can be monitored using the single server.