TCP connection check


 
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# 8  
Old 06-22-2011
Well what does it print?
# 9  
Old 06-23-2011
I put some info printing to my code in order to examine where function execution breaks. Now it lookes like that:
Code:
/***
 * Sends request through socket
 * Returns:
 *             0    success
 *             -1    buffer memory allocation failed
 */
int send_request(int socket, request_s *request) {
    char *buffer;

    if ((buffer = (char *) malloc(MSG_SIZE)) == NULL) {
        ERR("malloc");
        return -1;
    }
    int i;
    request_to_string(request, buffer);
    printf("send_request: before send\n");
    if ((i = send(socket, buffer, MSG_SIZE, 0)) < 0) {
        free(buffer);
        ERR("send");
    }
    printf("send_request: bytes sent: %d\n",i);
    printf("send_request: after send\n");
    free(buffer);
    return 0;
}
int communicate(int socket, request_s *request, response_s *response) {
    fd_set rfds;
    sigset_t mask, old_mask;
    char buffer[MSG_SIZE];
    memset(&buffer, 65, MSG_SIZE * sizeof(char));
    printf("communicate: beginning\n");
    if (request == NULL)
        return -1;
    else {
        if (send_request(socket, request) < 0) {
            printf("Sending request failed.\n");
            return -2;
        }
    }
    printf("communicate: after sending request\n");
    FD_ZERO(&rfds);
    FD_SET(socket, &rfds);
    sigemptyset(&mask);
    sigaddset(&mask, SIGINT);
    sigprocmask(SIG_BLOCK, &mask, &old_mask);

    if (pselect(socket + 1, &rfds, NULL, NULL, NULL, &old_mask) > 0) {
        if (FD_ISSET(socket, &rfds)) {
            if (TEMP_FAILURE_RETRY(recv(socket, (void *) buffer, MSG_SIZE, 0))
                    < 0)
                return -3;
            string_to_response(buffer, response);
            printf("communicate: buffer: %s\n", buffer);
            return 0;
        }
    }
    if (errno == EINTR) {
        request->type = MSG_EXIT_REQ;
        send_request(socket, request);
        TEMP_FAILURE_RETRY(close(socket));
        exit(EXIT_FAILURE);
    }
    return -4;
}

Here is also console output from client, when server is broken:
Code:
:~$ 5
send_scores_request: beginning
communicate: beginning
send_request: before send
send_request: bytes sent: 150
send_request: after send
communicate: after sending request
communicate: buffer: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
send_scores_request: after communicate
Invalid response from the server (not MSG_SCORES_RSP)
1 - Show board
2 - Show my tiles
3 - Check whose turn it is
4 - Make a move
5 - Show scores

6 - Exit

:~$ 5
send_scores_request: beginning
communicate: beginning
send_request: before send

Remarks:
1. Don't worry about those AAAAA... in buffer. I made memset(&buffer, 65...) at the beginning in order to better visualise if there something changes in the buffer, apparently not.
2. As you can see, menu position 5 has been invoked twice. As I said before, first time send does not return any error, also recv neither returns any error nor changes the buffer. Second time program quits.

It is a very strange situation. For now I don't even know where to find a mistake Smilie
# 10  
Old 06-23-2011
How about just printing the send() error rather than killing yourself in ERR() ?
# 11  
Old 06-23-2011
You haven't put an print statements in for recv() so we don't know how many bytes it received, if any.

Hmm... Perhaps you're off by one communication? As in, there's data sitting in the buffer that wasn't read last time? There's no guarantee you're going to get it all in one recv(), after all, you have to know how much is coming (or use a delimiter) to know when to stop.
# 12  
Old 06-23-2011
What I was getting at is, we haven't seen the socket setup but I'm assuming they're non-blocking TCP, so the first send() might put out 150 bytes, then you come around and get an error but the ERR() macro has a kill(0,SIGKILL) so you kill yourself before you print it to the terminal.
# 13  
Old 06-24-2011
Getting rid of ERR does not help, because this if ((send...) < 0) condition is never fulfilled. It looks like send() kills program. It sounds crazy.
I have put my whole code on github: https://github.com/chelmsford/Scrabble
Maybe you will find something what I can't see.

Last edited by Shang; 06-24-2011 at 10:53 AM..
# 14  
Old 06-24-2011
Try catching the SIGPIPE signal. You may be getting broken-pipe when you write to a broken socket.
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