Server And Client In Python And C

I've wrote a simple client code in python, and I'm trying to connect to a simple echo server written in C. I know it shouldn't matter, but for some reason I did manage to connect t

Solution 1:

(1) Add a listen call to the TCP section of the code.

(2) You have to tell accept what the length of the sockaddr you are passing it is and it will in return tell you the length of the address of the client it returned. You were passing it as 0 length so naturally it didn't pass back a client address which subsequently makes your gethostbyaddr fail with unknown address.

(3) If you don't close the client socket within the loop it just remains open (and leaks a file descriptor) for the duration of the server's life. Eventually you will run out of FDs. It doesn't effect your client which just closes after the receipt of one msg but any client who writes more than one message will never have it received by the server and will never receive an eof from the server.

if (port == ECHO_PORT_TCP)
{
    if (listen(echo_socket, ECHO_PORT_TCP) == -1)
    {
        perror("listen");
        exit(1);
    }

    while (1)
    {
        clientlen = sizeof(client);

        echo_socket_child = accept(echo_socket, (struct sockaddr *) &client, &clientlen);

        if (echo_socket_child < 0)
        {
              perror("accept"); 
              break; 
        }

        // gethostbyaddr: determine who sent the message
        hostp = gethostbyaddr((const char *) &client.sin_addr.s_addr, sizeof(client.sin_addr.s_addr), AF_INET);

        if (hostp == NULL)
        {   herror("byaddr"); 
            break;
        }

        hostaddrp = inet_ntoa(client.sin_addr);

        if (hostaddrp == NULL)
        {
            printf("ERROR on inet_ntoa\n");
            break;
        }

        printf("server established connection with %s (%s)\n", hostp->h_name, hostaddrp);

        bzero(buffer, BUFFER_SIZE);
        msg_byte_size = read(echo_socket_child, buffer, BUFFER_SIZE);

        if (msg_byte_size < 0)
        {
            printf("ERROR reading from socket");
            break;
        }

        printf("server received %d bytes: %s", msg_byte_size, buffer);

        msg_byte_size = write(echo_socket_child, buffer, strlen(buffer));

        if (msg_byte_size < 0)
        {
            printf("ERROR writing to socket");
            break;
        }

        close(echo_socket_child);

    } // endof while(1)

    return -1;
}