This example provides a sample program that uses the AF_UNIX address family. The AF_UNIX address family uses many of the same socket calls as other address families, except that it uses the path name structure to identify the server application.
/**************************************************************************/
/* This sample program provides code for a server application that uses */
/* AF_UNIX address family */
/**************************************************************************/
/**************************************************************************/
/* Header files needed for this sample program */
/**************************************************************************/
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
/**************************************************************************/
/* Constants used by this program */
/**************************************************************************/
#define SERVER_PATH "/tmp/server"
#define BUFFER_LENGTH 250
#define FALSE 0
void main()
{
/***********************************************************************/
/* Variable and structure definitions. */
/***********************************************************************/
int sd=-1, sd2=-1;
int rc, length;
char buffer[BUFFER_LENGTH];
struct sockaddr_un serveraddr;
/***********************************************************************/
/* A do/while(FALSE) loop is used to make error cleanup easier. The */
/* close() of each of the socket descriptors is only done once at the */
/* very end of the program. */
/***********************************************************************/
do
{
/********************************************************************/
/* The socket() function returns a socket descriptor representing */
/* an endpoint. The statement also identifies that the UNIX */
/* address family with the stream transport (SOCK_STREAM) will be */
/* used for this socket. */
/********************************************************************/
sd = socket(AF_UNIX, SOCK_STREAM, 0);
if (sd < 0)
{
perror("socket() failed");
break;
}
/********************************************************************/
/* After the socket descriptor is created, a bind() function gets a */
/* unique name for the socket. */
/********************************************************************/
memset(&serveraddr, 0, sizeof(serveraddr));
serveraddr.sun_family = AF_UNIX;
strcpy(serveraddr.sun_path, SERVER_PATH);
rc = bind(sd, (struct sockaddr *)&serveraddr, SUN_LEN(&serveraddr));
if (rc < 0)
{
perror("bind() failed");
break;
}
/********************************************************************/
/* The listen() function allows the server to accept incoming */
/* client connections. In this example, the backlog is set to 10. */
/* This means that the system will queue 10 incoming connection */
/* requests before the system starts rejecting the incoming */
/* requests. */
/********************************************************************/
rc = listen(sd, 10);
if (rc< 0)
{
perror("listen() failed");
break;
}
printf("Ready for client connect().\n");
/********************************************************************/
/* The server uses the accept() function to accept an incoming */
/* connection request. The accept() call will block indefinitely */
/* waiting for the incoming connection to arrive. */
/********************************************************************/
sd2 = accept(sd, NULL, NULL);
if (sd2 < 0)
{
perror("accept() failed");
break;
}
/********************************************************************/
/* In this example we know that the client will send 250 bytes of */
/* data over. Knowing this, we can use the SO_RCVLOWAT socket */
/* option and specify that we don't want our recv() to wake up */
/* until all 250 bytes of data have arrived. */
/********************************************************************/
length = BUFFER_LENGTH;
rc = setsockopt(sd2, SOL_SOCKET, SO_RCVLOWAT,
(char *)&length, sizeof(length));
if (rc < 0)
{
perror("setsockopt(SO_RCVLOWAT) failed");
break;
}
/****************************************************/
/* Receive that 250 bytes data from the client */
/****************************************************/
rc = recv(sd2, buffer, sizeof(buffer), 0);
if (rc < 0)
{
perror("recv() failed");
break;
}
printf("%d bytes of data were received\n", rc);
if (rc == 0 ||
rc < sizeof(buffer))
{
printf("The client closed the connection before all of the\n");
printf("data was sent\n");
break;
}
/********************************************************************/
/* Echo the data back to the client */
/********************************************************************/
rc = send(sd2, buffer, sizeof(buffer), 0);
if (rc < 0)
{
perror("send() failed");
break;
}
/********************************************************************/
/* Program complete */
/********************************************************************/
} while (FALSE);
/***********************************************************************/
/* Close down any open socket descriptors */
/***********************************************************************/
if (sd != -1)
close(sd);
if (sd2 != -1)
close(sd2);
/***********************************************************************/
/* Remove the UNIX path name from the file system */
/***********************************************************************/
unlink(SERVER_PATH);
}