The RtdRMPServer Class

The RtdRMPServer class overrides the above virtual methods, as well as providing many methods for dealing with server-specific processing. The server spawns a child process in order to carry out image processing prior to sending the image. This is so that RMP events may continue to be processed while the potentially rather long image compression takes place.

The child and parent processes are synchronised as follows: the server forks, with the parent process returning immediately to the RMP detect loop. The child process performs compression tasks, and on completion places the result into a separate buffer of shared memory before raising a semaphore. The child process then exits. The parent continually polls the semaphore, and when it detects that the child has completed sends the shared memory buffer to the clients. The semaphore is then decremented.

The RtdRMPServer class also implements the methods of the rtdrmpserver Tk widget, and as such overrides the TclCommand call() method. See TclCommand(3) and rtdrmpserver(n) for more information.

The following are the most important RtdRMPServer methods:

get_image() - called when the socket connection from the rtdServer becomes readable, this passes control to the send routines if it is time for an image to be sent,
send_image(rtdIMAGE_INFO *) - drives the main image processing and forking of the parent,
checkShm() - called by the parent to check the semaphore state, and send the data if it exists,
attach_server() - attach the eavesdrop server to the local server daemon to receive images,
processImageData(rtdIMAGE_INFO *) - return a Mem object for the buffer that is to be compressed. This routine also deals with extraction of image sub-regions, if this is required,
authenticateIPAddress(char *) - authenticate whether a given IP address is an allowed client,
killClient(char *) - send a message to a client address to shut the client down,
check_members(RMP_BOOL) - check the current group membership list against the allowed membership list,
.processServerMessage(RMPEvent *) - process a message sent from a client to the server.