Example Using UNIX Domain Stream Sockets

/*
 *      Sample Program: AF_UNIX stream sockets, server process
 *
 *      CATCH - RECEIVE DATA FROM THE PITCHER
 *
 *      Pitch and catch set up a simple unix domain stream socket
 *      client-server connection. The client (pitch) then sends
 *      data to server (catch), throughput is calculated, and the
 *      result is printed to the client's stdout.
 */
#include <stdio.h>
#include <time.h>
#include <signal.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#define SOCKNAME        "/tmp/p_n_c"
#define BUFSIZE         32*1024-1
int     timeout();
int     s;              /* server socket */
char buffer[BUFSIZE];
struct bullet {
     int bytes;
     int throughput;
     int magic;
} bullet = { 0, 0, 0 };
 
send_data(fd, buf, buflen)
     char *buf;
{
     int cc;
     while (buflen > 0) {
          cc = send(fd, buf, buflen, 0);
          if (cc == -1) {
               perror("send");
               exit(0);
          }
          buf += cc;
          buflen -= cc;
     }
}
recv_data(fd, buf, buflen)
     char *buf;
{
     int cc;
     while (buflen > 0) {
          cc = recv(fd, buf, buflen, 0);
          if (cc == -1) {
               perror("recv");
               exit(0);
          }
          buf += cc;
          buflen -= cc;
     }
}
main(argc, argv)
     int argc;
     char *argv[];
{
     int bufsize, bytes, cc, i, total, pid, counter_pid;
     float msec;
     struct timeval tp1, tp2;
     int ns, recvsize, secs, usec;
     struct timezone tzp;
     struct sockaddr_un sa;
/*
 * The SIGPIPE signal will be received if the peer has gone away
 * and an attempt is made to write data to the peer. Ignoring this
 * signal causes the write operation to receive an EPIPE error.
 * Thus, the user is informed about what happened.
*/
     signal(SIGPIPE, SIG_IGN);
     signal(SIGCLD, SIG_IGN);
     signal(SIGINT, timeout);
     setbuf(stdout, 0);
     setbuf(stderr, 0);
     if (argc > 1) {
          argv++;
          counter_pid = atoi(*argv++);
     } else
          counter_pid = 0;
/*
 * Set up the socket variables - address family, socket name.
 * They'll be used later to bind() the name to the server socket.
 */
     sa.sun_family = AF_UNIX;
     strncpy(sa.sun_path, SOCKNAME,
                    (sizeof(struct sockaddr_un) - sizeof(short)));
/*
 * Create the server socket
 */
     if ((s = socket( AF_UNIX, SOCK_STREAM, 0)) == -1) {
          perror("catch - socket failed");
          exit(0);
     }
     bufsize = BUFSIZE;
/*
 * Use setsockopt() to change the socket buffer size to improve
 * throughput for large data transfers
 */
     if ((setsockopt(s, SOL_SOCKET, SO_RCVBUF, &bufsize, 
sizeof(bufsize)))
          == -1) {
               perror("catch - setsockopt failed");
               exit(0);
     }
/*
 * Bind the server socket to its name
 */
     if ((bind(s, &sa, sizeof(struct sockaddr_un))) == -1) {
          perror("catch - bind failed");
          exit(0);
     }
/*
 * Call listen() to enable reception of connection requests
 * (listen() will silently change given backlog 0, to be 1 instead)
 */
     if ((listen(s, 0)) == -1) {
          perror("catch - listen failed");
          exit(0);
     }next_conn:
     i = sizeof(struct sockaddr_un);
/*
 * Call accept() to accept connection request. This call will block
 * until a connection request arrives.
 */
     if ((ns = accept(s, &sa, &i)) == -1) {
          if (errno == EINTR)
               goto next_conn;
          perror("catch - accept failed");
          exit(0);
     }
     if ((pid = fork()) != 0) {
          close(ns);
          goto next_conn;
     }
/*
     close(s);
*/
/*
 * Receive the bullet to synchronize with the other side
 */
     recv_data(ns, &bullet, sizeof(struct bullet));
     if (bullet.magic != 12345) {
          printf("catch: bad magic %d\n", bullet.magic);
          exit(0);
     }
     bytes = bullet.bytes;
     recvsize = (bytes>BUFSIZE)?BUFSIZE:bytes;
/*
 * Send the bullet back to complete synchronization
 */
     send_data(ns, &bullet, sizeof(struct bullet));
     cc = 0;
     if (counter_pid)
          kill(counter_pid, SIGUSR1);
     if (gettimeofday(&tp1, &tzp) == -1) {
          perror("catch time of day failed");
          exit(0);
     }
/*
 * Receive data from the client
 */
     total = 0;
     i = bytes;
     while (i > 0) {
          cc = recvsize < i ? recvsize : i;
          recv_data(ns, buffer, cc);
          total += cc;
          i -= cc;
     }
/*
 * Calculate throughput
 */
     if (gettimeofday(&tp2, &tzp) == -1) {
          perror("catch time of day failed");
          exit(0);
     }
     if (counter_pid)
          kill(counter_pid, SIGUSR2);
     secs = tp2.tv_sec - tp1.tv_sec;
     usec = tp2.tv_usec - tp1.tv_usec;
     if (usec < 0) {
          secs ;
          usec += 1000000;
     }
     msec = 1000*(float)secs;
     msec += (float)usec/1000;
     bullet.throughput = bytes/msec;
/*
 * Send back the bullet with throughput info, then close the
 * server socket
 */
     if ((cc = send(ns, &bullet, sizeof(struct bullet), 0)) == -1) {
          perror("catch - send end bullet failed");
          exit(0);
     }
     close(ns);
}
timeout()
{
        printf( "alarm went off -- stopping the catch process\n");
        fprintf(stderr, "stopping the catch process\n");
        unlink(SOCKNAME);
        close(s);
        exit(6);
}
/*
*       Sample Program : AF_UNIX stream sockets, client process
*
*       PITCH - SEND DATA TO THE CATCHER
*
*       Pitch and catch set up a simple unix domain stream socket
*       client-server connection. The client (pitch) then sends
*       data to the server (catch), throughput is calculated, and
*       the result is printed to the client's stdout.
*/
#include <stdio.h>
#include <time.h>
#include <netdb.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#define SOCKNAME    "/tmp/p_n_c"
#define BUFSIZE          32*1024-1
char buffer[BUFSIZE];
struct bullet {
     int bytes;
     int throughput;
     int magic;
} bullet = { 0, 0, 12345 };
send_data(fd, buf, buflen)
     char *buf;
{
     int cc;
     while (buflen > 0) {
          cc = send(fd, buf, buflen, 0);
          if (cc == -1) {
               perror("send");
               exit(0);
          }
          buf += cc;
          buflen -= cc;
     }
}
recv_data(fd, buf, buflen)
     char *buf;
{
     int cc;
     while (buflen > 0) {
          cc = recv(fd, buf, buflen, 0);
          if (cc == -1) {
               perror("recv");
               exit(0);
          }
          buf += cc;
          buflen -= cc;
     }
}
main( argc, argv)
     int argc;
     char *argv[];
{
     int bufsize, bytes, cc, i, total, pid;
     float msec;
     struct timeval tp1, tp2;
     int s, sendsize, secs, usec;
     struct timezone tzp;
     struct sockaddr_un sa;
/*
 * The SIGPIPE signal will be received if the peer has gone away
 * and an attempt is made to write data to the peer.  Ignoring
 * the signal causes the write operation to receive an EPIPE error.
 * Thus, the user is informed about what happened.
*/
signal(SIGPIPE, SIG_IGN);
     setbuf(stdout, 0);
     setbuf(stderr, 0);
     if (argc < 2) {
          printf("usage: pitch Kbytes [pid]\n");
          exit(0);
     }
     argv++;
/*
 * Set up socket variables (address family; name of server socket)
 * (they'll be used later for the connect() call)
 */
     sa.sun_family = AF_UNIX;
     strncpy(sa.sun_path, SOCKNAME,
                (sizeof(struct sockaddr_un) - sizeof(short)));
     bullet.bytes = bytes = 1024*atoi(*argv++);
     if (argc > 2)
          pid = atoi(*argv++);
     else
          pid = 0;
     sendsize = (bytes < BUFSIZE) ? bytes : BUFSIZE;
/*
 * Create the client socket
 */
     if ((s = socket( AF_UNIX, SOCK_STREAM, 0)) == -1) {
          perror("pitch - socket failed");
          exit(0);
     }
     bufsize = BUFSIZE;
/*
 * Change the default buffer size to improve throughput for
 * large data transfers
 */
     if ((setsockopt(s, SOL_SOCKET, SO_SNDBUF, &bufsize, 
sizeof(bufsize)))
          == -1) {
               perror("pitch - setsockopt failed");
               exit(0);
     }
/*
 * Connect to the server
 */
     if ((connect(s, &sa, sizeof(struct sockaddr_un))) == - 1) {
          perror("pitch - connect failed");
          exit(0);
     }
/*
 * send and receive the bullet to synchronize both sides
 */
     send_data(s, &bullet, sizeof(struct bullet));
     recv_data(s, &bullet, sizeof(struct bullet));
     cc = 0;
     if (pid)
          kill(pid,SIGUSR1);
     if (gettimeofday(&tp1, &tzp) == -1) {
          perror("pitch time of day failed");
          exit(0);
     }
     i = bytes;
     total = 0;
/*
 * Send the data
 */
     while (i > 0) {
          cc = sendsize < i ? sendsize : i;
          send_data(s, buffer, cc);
          i -= cc;
          total += cc;
     }
/*
 * Receive the bullet to calculate throughput
 */
     recv_data(s, &bullet, sizeof(struct bullet));
     if (gettimeofday(&tp2, &tzp) == -1) {
          perror("pitch time of day failed");
          exit(0);
     }
     if (pid)
          kill(pid, SIGUSR2);
/*
 * Close the socket
 */
     close(s);
     secs = tp2.tv_sec - tp1.tv_sec;
     usec = tp2.tv_usec - tp1.tv_usec;
     if (usec < 0) {
          secs;
          usec += 1000000;
     }
     msec = 1000*(float)secs;
     msec += (float)usec/1000;
     printf("PITCH: %d Kbytes/sec\n", (int)(bytes/msec));
     printf("CATCH: %d Kbytes/sec\n", bullet.throughput);
     printf("AVG:   %d Kbytes/sec\n", 
 ((int)(bytes/msec)+bullet.throughput)/2);
}