Example of a socket read/write pattern

example_sockets.c

// Start
listen_fd = socket()...bind()...
client_fd = -1;

// Main loop
FD_SET(listen_fd,readfds);

if(client_fd != -1)
    FD_SET(client_fd,readfds);

N = listen_fd + 1;

if(client_fd > listen_fd)
    N = client_fd + 1;   /* stupid semantics require N to be one more than the highest fd to wait for */

struct timeval tv = { 0,0}; /* timeout: 0 seconds, 0 microseconds */
i = select(N,&readfds,NULL,NULL,tv);

if(FD_ISSET(readfds,listen_fd)){
    i = accept(listen_fd);
    if(client_Fd == -1)
       close(i);   /* we already have a client, close connection immediately */
   else
       client_fd = i;
}

if(client-Fd != -1 && FD_ISSET(client_fd,readfds)){
    char c;
    i = read(client_fd,&c,1)); /* read a single byte */
   if(c == START_BYTE)...
   if(c == STOP_BYTE)...
}

// Final block
if(i== 0 /* 0 byte read == EOF */){
     close(client_fd);
     client_Fd = -1;
}
if(i == -1){ /* error?! */
    perror("client_Read");
   close(client_fd);
   client_fd = -1;
}

This is an example of a read/write pattern for sockets shared by Chris via IM.