Start the resource manager message loop

/* start the resource manager message loop */
while(1) {
    if(dispatch_handler == NULL) {
        fprintf(stderr, "block error\n");
        return EXIT_FAILURE;
    }
    dispatch_handler(ctp);
}

Once the resource manager establishes its name, it receives messages when any client program tries to perform an operation (e.g., open(), read(), write()) on that name.

fd = open ("/dev/sample", O_RDONLY);

the client's C library constructs an _IO_CONNECT message and sends it to our resource manager. Our resource manager receives the message within the dispatch_block() function. We then call dispatch_handler(), which decodes the message and calls the appropriate handler function based on the connect and I/O function tables that we passed in previously. After dispatch_handler() returns, we go back to the dispatch_block() function to wait for another message.

read (fd, buf, BUFSIZ);