source: fact/tools/SocketClient/ExampleServer.cc@ 20109

/********************************************************************\

  Example socket server

  Code from original drsdaq socket thread
  
  This code will block execution in the accept() and read() socket function
  while waiting for a connection or data. To terminate, these blocking functions
  must be interrupted by raising a signal (e.g. SIGUSR1). Testing on errno=EINTR
  then indicates this.
  
  Oliver Grimm, May 2010
  
\********************************************************************/

#define PORT 2000               // TCP/IP port

void CCCommand() {

  int ServerSocket,ConnectionSocket,ReadResult;
  struct sockaddr_in SocketAddress, ClientAddress;
  struct hostent *ClientName;
  socklen_t SizeClientAddress=sizeof(ClientAddress);
  char Command[MAX_COM_SIZE];

  // Set up server socket
  if ((ServerSocket = socket(PF_INET, SOCK_STREAM, 0)) == -1) {
    printf("Could not open server socket (%s)\n", strerror(errno));
    return;
  }
  // Allows immediate reuse of socket after closing (circumvents TIME_WAIT)
  int Value=1;
  if (setsockopt(ServerSocket, SOL_SOCKET, SO_REUSEADDR, (char *) &Value, sizeof (Value)) == -1) {
    printf("Warning: Could not set server socket option SO_REUSEADDR (%s)\n", strerror(errno));
  }

  SocketAddress.sin_family = PF_INET;
  SocketAddress.sin_port = htons((unsigned short) PORT);
  SocketAddress.sin_addr.s_addr = INADDR_ANY;

  if (bind(ServerSocket, (struct sockaddr *) &SocketAddress, sizeof(SocketAddress)) == -1)
  {
    printf("Could not bind port to socket (%s)\n", strerror(errno));
    close(ServerSocket);
    return;
  }
  if (listen(ServerSocket, 0) == -1) {
    printf("Could not set socket to listening (%s)\n", strerror(errno));
    close(ServerSocket);
    return;
  }
  
  // Looping to wait for incoming connection  
  while (true) {  
    if ((ConnectionSocket = accept(ServerSocket, (struct sockaddr *) &ClientAddress, &SizeClientAddress)) == -1) {
      if (errno!=EINTR) printf("Failed to accept incoming connection (%s)\n", strerror(errno));
      close(ServerSocket);
      return;
    }

    ClientName = gethostbyaddr((char *) &ClientAddress.sin_addr ,sizeof(struct sockaddr_in),AF_INET);
    printf("Connected to client at %s (%s).\n", inet_ntoa(ClientAddress.sin_addr), ClientName!=NULL ? ClientName->h_name:"name unknown");

    // Looping as long as client exists and program not terminated
    while (true) {

      // Try to read command from socket
      memset(Command, 0, sizeof(Command));
      ReadResult = read(ConnectionSocket, Command, MAX_COM_SIZE);
      if (ReadResult == 0) break;  // Client not exisiting anymore
      if (ReadResult == -1) {
                if (errno!=EINTR) printf("Error read from socket (%s)\n", strerror(errno));
                break;
      }
      if (Command[strlen(Command)-1]=='\n') Command[strlen(Command)-1]='\0';  // Remove trailing newline
      
      printf("Received command '%s'\n", Command);
    }

    printf("Disconnected from client.\n");
    close(ConnectionSocket);
  } 
  close(ServerSocket);
  printf("Server socket closed.\n");
}