Question

I got this code from Andy Tanenbaum’s book. I am trying to run it. It compiles and waits for connection. But when I type localhost:886, I see no effect either in the browser or the terminal. (It should echo a new connection string as per the code).

#define     SERVER_PORT         886     /* The port at which the server listens */
#define     BUF_SIZE        64032       /* The size of buffer for request and response */
#define     QUEUE_SIZE      10      /* Block transfer size */


int main (int argc, char* argv[]) {

    int     sock = 0, bnd = 0, lst = 0, fd = 0, sa = 0, bytes = 0, on = 1, conn_count = 0;
    char    buf[BUF_SIZE];
    struct  sockaddr_in channel;            /* IP address holder */

    /* The address structure that binds with the socket */

    memset (&channel, 0, sizeof(channel));

    channel.sin_family      =   AF_INET;
    channel.sin_addr.s_addr     =   htonl (INADDR_ANY);
    channel.sin_port        =   htons (SERVER_PORT);

    /* Parital opening of the socket, while waiting for connection */

    sock                =   socket (AF_INET, SOCK_STREAM, IPPROTO_TCP); /* Creates a new socket */
    if (sock < 0)
        printf ("Partial opening of the socket failed! Error: %d", sock);

    setsockopt (sock, SOL_SOCKET, SO_REUSEADDR, (char *) &on, sizeof(on));

    bnd             =   bind (sock, (struct sockaddr *) &channel, sizeof(channel));
    if (bnd < 0)
        printf ("Binding failure! Error: %d", bnd);

    lst             =   listen (sock, QUEUE_SIZE);
    if (lst < 0)
        printf ("Unable to listen on the socket! Error: %d", lst);

    /* The socket has been set-up. Wait for the connection and process it. */

    while (1) {

        conn_count      +=  1;
        printf ("Received connection: %d", conn_count); 
        sa          =   accept (sock, 0, 0);
        if (sa < 0)
            puts ("Unable to accept the socket opened for connection.");

        read (sa, buf, BUF_SIZE);

        puts (buf);     /* Output the string to the screen */

        close (sa);
    }
}

Answer 1

Are you running this as sudo/root? Your bind() might be failing because it is using privileged port.

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[update from comment:]

Privileged ports are all ports below 1024.