select always returns -1 while trying to read from socket and stdin

Posted by Aleyna on Stack Overflow See other posts from Stack Overflow or by Aleyna
Published on 2010-04-25T01:27:45Z Indexed on 2010/04/25 1:33 UTC
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Hello

I have the following code implemented on C++(Linux) to check on my listening socket and stdin using select. select however keeps returning -1 no matter what I try to do! What's wrong with that code :s I will appreciate any help. Thanks

highsock = m_sock; //listening socket

memset((char *) &connectlist, 0, sizeof(connectlist));
memset((char *) &socks, 0, sizeof(socks));

int readsocks;
struct timeval timeout;
timeout.tv_sec = 60;
timeout.tv_usec = 0;

while (1) {
    updateSelectList();
    //cout << "highest sock: " << highsock << endl;
    tempreadset = readset;
    readsocks = select(highsock+1, &tempreadset, NULL, NULL, &timeout);
    //cout << "# ready: " << readsocks << endl;
    if (readsocks < 0) {
        if (errno == EINTR)
            continue;
        cout << "select error" << endl;
    }
    if (readsocks > 0) {
        readFromSocks();
    }
}

void readFromSocks() {
    if (FD_ISSET(STDIN, &readset)) {
    ...
    } else if (FD_ISSET(m_sock, &readset)) {
    ...
    }
}

void updateSelectList() {
    FD_ZERO(&readset);

    FD_SET(STDIN, &readset);
    FD_SET(m_sock, &readset);

    for (int i=0; i<MAXCONNECTIONS; i++) {
        if (connectlist[i] != 0) {
            FD_SET(connectlist[i], &readset);
            if (connectlist[i] > highsock)
                highsock = connectlist[i];
        }
    }

    highsock = max(max(m_sock, STDIN), highsock);
}

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