Abstract:
Methods, apparatus, systems and computer program product for updating a user session in a terminal server environment. Transfer of display data corresponding to an updated user interface can occur via a memory shared between an agent server and an agent client in a terminal server environment. Access to the shared memory can be synchronized via token passing or other operation to prevent simultaneous access to the shared memory. Token sharing and synchronized input/output can be performed using FIFOs, sockets, files, semaphores and the like, allowing communications between the agent server and agent client communications to adapt to different operating system architecture.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of provisional patent application Ser. No. 61/099,485, filed Sep. 23, 2008, which is incorporated by reference. 
    
    
     FEDERALLY SPONSORED RESEARCH 
     Not applicable. 
     SEQUENCE LISTING OR PROGRAM 
     Not applicable. 
     FIELD OF THE INVENTION 
     The invention relates to the field of computer networks. In particular, the present invention relates to methods, apparatus, systems and computer program product for updating a user session in a terminal server environment. 
     BACKGROUND 
     For enterprises large and small, consolidation of hardware and software is increasingly vital due to reasons of accessibility, reliability, data security, cost and the administration of applications and the network itself. Managing remote users, their computing experience and their access to networks is similarly crucial. Many different types of institutions have used terminal server applications to provide a computing environment and to address these issues, despite having varied institutional and computing objectives. For instance, educational institutions deploy computer networks to allow teachers, students and staff to connect remotely, thereby allowing increased productivity, easier access to information, rapid communication and, ultimately, enhanced learning opportunities. Government agencies are perhaps more concerned with data security, which is why terminal services always have been essential to their information technology infrastructures. Thin client and network deployments have been mandated in several agencies—this allows all operations to be performed centrally, and secures and monitors information that may have been sent or received. Commercial organizations, as well, benefit from deploying terminal servers so that data transmission can be managed and controlled; for example, by requiring users to access data through smart cards and biometrics, and allowing editing and review of the data only within a secure environment, or by certain identified users. And in the case of organizations of all types there is a growing need for network users to access information via mobile or handheld devices from remote locations. 
     Centralized computing results in cost savings, ease of administration and enhanced security. Since almost all the processing of an application is done on a central server, companies are not forced to continuously upgrade or replace client or user hardware to keep pace with the systems requirements of modern applications. Maintenance of applications is isolated to the application server and not each individual node, also reducing administrative overhead. Servers are usually located in secure data centers, reducing the risk of physical theft. Centralized malware and audit processes also facilitate enhanced security. In addition, replacing workstations with thin clients can reduce energy consumption, environmental costs, support cost, and hardware costs. 
     In certain terminal server environments, however, implementing multiple independent instances of applications to satisfy the demands of remote clients leads to issues in being able to securely and synchronously update the graphical display of server output. Simply transmitting the output from certain output agents, such as via window server, for example, may lead to information being passed across user session boundaries, as the graphical data available would be that created by the most recent client session to access the application. As a result, a need exists for an improved method for updating graphical display information securely and in a timely fashion in a terminal server environment. There is also a need for an improved means to transport data from a user&#39;s session in a terminal server environment, allowing improved communications with a remote device. 
     SUMMARY 
     The disclosed embodiments relate to methods, apparatus, systems and computer program product for updating a user session in a terminal server environment. In accordance with a preferred embodiment, the disclosed methods, apparatus, systems and computer program product allow faster and less-error-prone transfer of display data corresponding to an updated user interface via a memory shared between an agent server and an agent client in a terminal server environment. This shared server-client arrangement is sometimes described herein as a “KVM agent” server/client system (referring to keyboard, video and mouse). In certain embodiments, accessing the shared memory is synchronized via token passing or other operation to prevent simultaneous access to the shared memory. In certain embodiments, this token sharing and synchronized input/output can be performed using FIFO pipes, sockets, files, semaphores and the like, allowing communications between the agent server and agent client communications to adapt to different operating system architecture. In a preferred embodiment, the agent pair implementation is protocol independent. Thus, among the advantages disclosed herein, one or more aspects are to provide a faster and more robust computing environment. Other advantages relate to an improved ability to transfer large amounts of display-associated data. These and other advantages of the many aspects of the disclosed embodiments will become apparent from a review of the following description and corresponding figures. 
    
    
     
       DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
         FIG. 1  is a graphical depiction of an exemplary computer network according to one embodiment of the disclosure. 
         FIG. 2  is a flow chart of an exemplary process for providing video data to a remote device. 
         FIGS. 3A-B  are graphical depictions of user interface instances exemplifying the use of dirty rectangles to indicate areas of change to a user interface. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments of the present invention are now described in detail, including depiction of the hardware components which serve as the context for the process embodiments. 
       FIG. 1  shows an example computer network  100 , which can include architectural elements corresponding to at least one input and/or output of a user context (or session). In some implementations, the computer network  100  can include a host system  126 . An operating system  102  can be executed on the host system  126 , the operating system  102  including one or more of a user context  104 , a KVM agent server  106 , a KVM agent client  110 , a protocol translator  108 , and a host communication socket  112 . The host system  126  also can include, a memory component  122 , which is accessible to the operating system  102  and the user context  104 . The computer network  100  further can include a remote system  124 . The remote system  124  can include one or more of a remote communications socket  116 , an output device  118 , such as a display and/or speakers, and at least one input device  120 , such as a keyboard and/or mouse. The remote system  124  and the host system  126  can communicate over a shared network  114 , which can be a public network, e.g. the Internet, a private network, e.g. a Local Area Network (LAN), or a combination thereof. 
     The remote system  124  can be any computing system configurable to communicate over the shared network  114 , such as a desktop computer, a laptop computer, a palm top computer, a server, a mobile communications device, and an embedded computing system. The remote system  124  can receive input and provide output through the input device  120  and the output device  118 . Further, the remote system  124  can be configured to communicate with the shared network  114  through a wired or wireless connection. 
     The host system  126  also can be any computing system configurable to communicate over the shared network  114 , such as a desktop computer, a laptop computer, a palm top computer, a server, a mobile communications device, and an embedded computing system. The operating system  102  can be executed on the host system  126 , and can be configured to provide an application environment in which one or more application programs can be executed. For example, the operating system  102  can be a Mac OS provided by Apple Inc. of Cupertino, Calif., a Windows operating system provided by Microsoft Corporation of Redmond, Wash., or a Linux operating system. In some implementations, the host system  126  can act as a server for the remote system  124 . Further, the host system  126  can be separated from the remote system  124  by any distance. For example, the remote system  124  can be a desktop computer located at an employee&#39;s home and the host system  126  can be a server located at an employer&#39;s site. 
     The user context  104 , which in some implementations can be referred to as a user session or a graphical session, can be configured as a single environment in which the user can access one or more functions of the operating system. A single user context is shown in  FIG. 1 , but the operating system  102  can be configured to host multiple user contexts. In some implementations, each user context, such as the user context  104 , is kept separate from all other existing user contexts. For example, separate memory utilization, file system access, and/or process execution can be maintained for each user context. In this way, actions and/or functions associated with one user context can be isolated to reduce their impact on one or more other existing user contexts and the host operating system. It will be appreciated that some actions taken in one user context can affect one or more other user contexts. For example, use of system resources by one user context can directly or indirectly reduce the system resources available to one or more other user contexts. In another example, a user context can be given special privileges to monitor or interact with one or more other user contexts, such as for maintenance purposes. 
     The KVM agent server  106  and the KVM agent client  110  can provide remote input and output for a user context  104  hosted by the operating system  102 . For example, the KVM agent server  106  and the KVM agent client  110  can provide one or more of a control device input, such as a keyboard and/or mouse, an audio output, an image output, and/or a video output. The KVM agent client  110  and the KVM agent server  106  further can be configured to transmit information into and/or out of a user context, such as the user context  104 . In some implementations, the amount of data used to represent an input and/or an output can be small, such as keyboard input, mouse input, or an audio output representing a beep. This data can be passed from the KVM agent client  110  to the KVM agent server  106  directly using a software construct, such as a socket, pipe, port, FIFO, or inter-process message passing, e.g. Mach, without significantly impacting the operating system  102  or the host system  126 . Further, the message passing can be performed serially and asynchronously, such that the messages are passed in the correct order. The objects sending and/or receiving information can be idle between messages. In one example, key presses of A, B, and C can be passed and received in the order “A, B, C.” 
     In some implementations, the amount of data used to represent an input and/or an output, such as biometric, video, or streaming audio data, can be too large for passing using a software construct, such as a socket, pipe, port or inter-process message passing. For example, the video data associated with a twenty-inch computer monitor can take up to forty seconds to be passed by software running on a modern hardware architecture. Many computer monitor screens can refresh at a rate of sixty times per second. Accordingly, direct message passing between the KVM agent client  110  and the KVM agent server  106  cannot accommodate the amount of data associated with video. 
     Large amounts of input and/or output data can be passed between the KVM agent server  106  and the KVM agent client  110  by way of shared memory  122 . Shared memory software tools such as Universal Pages Lists (UPL), POSIX, SYSV, the Unix environment program “pmap” and the X is not Unix (XNU) environment programs “MachVM” and “VM” can be used to share memory between the KVM agent client  110  and KVM agent server  106 . Further, metadata corresponding to the shared memory can be transmitted between the KVM agent client  110  and KVM agent server  106 . For example, the metadata can be transmitted via a socket, FIFO pipe or port. The metadata can describe any aspect of the shared memory, including what data is stored in the shared memory and the order in which the data is stored. 
     The protocol translator  108  can be configured to translate input and output data associated with the KVM agent client  110  into a protocol that can be utilized by a remote client, such as the Virtual Network Computer (VNC) protocol, the Remote Desktop Protocol (RDP), or the X11 protocol. The protocol translator  108  can communicate with one or more remote clients via the host communication socket  112 . For example, a connection between the host communication socket  112  and the remote communication socket  116  can be established over a communication network, such as the shared network  114 . Communications between the host communication socket  112  and the remote communication socket  116  can be serial and asynchronous, such that the messages are passed in the correct order and the objects sending and receiving information can be idle during the time between messages. Output data can be presented through the output device  118 . In some implementations, the output device  118  can be a computer monitor, a speaker, a projector, or other device appropriate for outputting data generated by the operating system  102 . Further, input data can be entered using the input device  120 , which can be a keyboard, a mouse, a touch screen, a keypad, a joystick, a touch pad, or other device appropriate for receiving input, directly or indirectly, from a user. 
       FIG. 2  shows a flow chart of an example process ( 200 ) for providing video data to a remote device. Video data associated with a user context executing in an operating system can change ( 202 ) in response to many circumstances. For example, with respect to a user interface corresponding to a user context, the time presented by a clock can be incremented, a cursor can move to a new position, or data associated with an application can be altered. A KVM agent server associated with the user context can determine ( 204 ) which sections of the user interface have been updated. In some implementations, sections of a user interface that have been updated can be designated as rectangular spaces and can be referred to as ‘dirty rectangles’. 
     An updated representation of the user interface for a user context and information corresponding to one or more dirty rectangles can be stored in a shared memory location ( 206 ). A KVM agent client can be configured to monitor the shared memory location and detect changes ( 208 ). When a change is detected, the KVM agent client can access the dirty rectangle information and transmit display information to a remote device ( 210 ) for presentation. In some implementations, information corresponding to the dirty rectangles can be transmitted. In other implementations, updated display information can be transmitted. The dirty rectangle information and/or updated display information can be transmitted via shared memory or a communications path, such as a socket, a pipe, a port, or messaging infrastructure. The client monitor can be associated with a remote system and can communicate with the operating system via a shared network, such as the Internet or a LAN. The output presented on the client monitor can be updated based on the dirty rectangles, so that only the portion of the interface that has changed is updated. 
       FIG. 3A  shows a plurality of user interface instances presented on a display, such as a display associated with a remote computing system. The user interface instance  302  precedes temporally the user interface instance  304 . For example, the user interface instances  302  and  304  can represent the display of a computer monitor which receives one or more output signals from an operating system. Further, the operating system generating the output signals can be executing on a computing system that is remote from the computing system to which the computer monitor is connected. 
     In the user interface instance  302 , a photo application window  320  is presented above a music application window  322 . Further, the photo application window  320  overlaps with, and thus partially obscures, the music application window  322 . Additionally, a mouse cursor  324  is presented in the user interface instance  302  such that it is positioned over a music program icon  326 . In the user interface instance  304 , the mouse cursor  324  and the music program icon  326  are highlighted, such as in response to a mouse click. Rectangles  310  and  312  can be generated by the operating system to represent a minimum bounding box around the mouse cursor  324  and the music program icon  326 . The rectangles  310  and  312  are illustrative of the areas in which the user interface instance has changed, as determined by the operating system, and are not displayed on the computer monitor. These rectangles  310  and  312  represent dirty rectangles that indicate areas of change to the user interface. Thus, the rectangles  310  and  312  represent the change between the user interface instance  302  and the user interface instance  304 . 
     In some implementations, the rectangles  310  and  312  also can be optimized. For example, the rectangles  310  and  312  can be combined to form one larger rectangle, such as by expanding one or more borders to form a single rectangle. In another example, two or more rectangles can be used to represent a single, nonrectangular shape. The two or more rectangles can be specified to minimize the portion of the user interface covered by the rectangles that has not changed. In some other implementations, nonrectangular shapes also can be used. 
     For example, input such as the click of a mouse may be made on the input device  120  of  FIG. 1 . The remote system  124  can send this input information through the socket  116 , through the network  114  to the socket  112 . The input information then can be passed from the socket  112  to the protocol translator  108 , which can translate the input information and pass it to the KVM agent client  110 . The KVM agent client  110  can then pass the input to the KVM agent server  106 . 
     In this example, the user interface information can be updated from the user interface instance  302  to the user interface instance  304 . The information related to the dirty rectangles  310  and  324  can be sent from the KVM agent server  106  to the memory  122 . The KVM agent client  110  can detect change to the information stored in the memory  112  and can pass the dirty rectangle information to the protocol translator  108 . The protocol translator  108  can translate the dirty rectangle information and can send it through the socket  112  to the shared network  114 . The dirty rectangle information can then be routed over the shared network  114 , through the socket  116 , to the remote client  124 . The remote client  124  can use the dirty rectangle information to generate an updated interface for display on the output device  118 . In other embodiments, updated display information can be transmitted from the host system  126  to the remote system  124 , based on the dirty rectangles. 
       FIG. 3B  shows a plurality of user interface instances presented on a display, such as a display associated with a remote computing system. The user interface instance  306  precedes temporally the user interface instance  308 . The difference between the user interface instances  304  and  306  is illustrated by the rectangle  314 . The operating system can cause the music application window  322  to be displayed in front of the photo application window  320 , such as in response to a mouse click selecting the music application icon  326 . Thus, the music application window  322  now partially obscures the photo application window  320 . The operating system further can generate video output data to update only to the section of the display at which the change in overlap, represented by the rectangle  314 , has occurred. The video output data generated can be passed to the remote client  124  to be displayed on the output device  118  as previously described. 
     In one example of desktop computing use, the area of a display output that is changed from one user interface instance to the next can be a small percentage of the total display area, such as 10%. However, the display output may not change between some user interface instances, for example if there is no input and the operating system does not change any of the displayed features. Alternatively, a large portion of the display output may change between some user interface instances. For example, an application launched in full screen mode can cause the entire display to change. 
     A rectangle, or other shape, defining an area of change can be expressed using a number of different conventions. For example, a rectangle can be defined by (X, Y, Height, Width), where X represents the distance between the lower left corner of a rectangle and the left side of the screen, Y represents the distance between the lower left corner of a rectangle and the bottom of the screen, Height represents the height of the rectangle, and Width represents the width of the rectangle. In another example, a rectangle, or other shape, can be defined by (X1, Y1, X2, Y2), where X1,Y1 represents the coordinates of the upper left corner of the rectangle and X2,Y2 represents the lower right corner of the rectangle. Any other system for expressing an object location also can be used. 
     In some implementations, information defining an area of change can be stored in the memory  122  along with the output information of the dirty rectangles  310 ,  312 , or  314 . The information defining an area of change can be used to generate information for updating a display or other such output. For example, the protocol translator  108  and/or the remote system  124  can modify an output of a user interface instance in accordance with an identified dirty rectangle. 
     The embodiments described above are given as illustrative examples only. It will be readily appreciated by those skilled in the art that many deviations may be made from the specific embodiments; accordingly, the scope of the invention is to be determined by the claims below rather than being limited to the specifically described embodiments above. In addition, the flowcharts found in the figures are provided to instruct a programmer of ordinary skill to write and debug the disclosed embodiments without undue effort; the logic flow may include other steps and the system other components. The invention is not limited to a particular expression of source or object code. Accordingly, other implementations are within the scope of the claims.