/*************************************************************************\
*                  Copyright (C) Michael Kerrisk, 2018.                   *
*                                                                         *
* This program is free software. You may use, modify, and redistribute it *
* under the terms of the GNU General Public License as published by the   *
* Free Software Foundation, either version 3 or (at your option) any      *
* later version. This program is distributed without any warranty.  See   *
* the file COPYING.gpl-v3 for details.                                    *
\*************************************************************************/

/* Listing 57-3 */

/* us_xfr_sv.c

   An example UNIX stream socket server. Accepts incoming connections
   and copies data sent from clients to stdout.

   See also us_xfr_cl.c.
*/
#include "us_xfr.h"
#define BACKLOG 5

int
main(int argc, char *argv[])
{
    struct sockaddr_un addr;
    int sfd, cfd;
    ssize_t numRead;
    char buf[BUF_SIZE];

    sfd = socket(AF_UNIX, SOCK_STREAM, 0);
    if (sfd == -1)
        errExit("socket");

    /* Construct server socket address, bind socket to it,
       and make this a listening socket */

    /* For an explanation of the following check, see the errata notes for
       pages 1168 and 1172 at http://www.man7.org/tlpi/errata/. */

    if (strlen(SV_SOCK_PATH) > sizeof(addr.sun_path) - 1)
        fatal("Server socket path too long: %s", SV_SOCK_PATH);

    if (remove(SV_SOCK_PATH) == -1 && errno != ENOENT)
        errExit("remove-%s", SV_SOCK_PATH);

    memset(&addr, 0, sizeof(struct sockaddr_un));
    addr.sun_family = AF_UNIX;
    strncpy(addr.sun_path, SV_SOCK_PATH, sizeof(addr.sun_path) - 1);

    if (bind(sfd, (struct sockaddr *) &addr, sizeof(struct sockaddr_un)) == -1)
        errExit("bind");

    if (listen(sfd, BACKLOG) == -1)
        errExit("listen");

    for (;;) {          /* Handle client connections iteratively */

        /* Accept a connection. The connection is returned on a new
           socket, 'cfd'; the listening socket ('sfd') remains open
           and can be used to accept further connections. */

        cfd = accept(sfd, NULL, NULL);
        if (cfd == -1)
            errExit("accept");

        /* Transfer data from connected socket to stdout until EOF */

        while ((numRead = read(cfd, buf, BUF_SIZE)) > 0)
            if (write(STDOUT_FILENO, buf, numRead) != numRead)
                fatal("partial/failed write");

        if (numRead == -1)
            errExit("read");

        if (close(cfd) == -1)
            errMsg("close");
    }
}