linux上的unix域套接字？

$./server1 
$

$./client1 
MESSAGE FROM SERVER: hello from a client

我希望服务器从客户端和客户端打印消息hello以从服务器打印hello.

我的操作系统和编译器如下：

$uname -a                                                                                                    
Linux temeraire 2.6.37.6-smp #2 SMP Sat Apr 9 23:39:07 CDT 2011 i686 Intel(R) Xeon(R) CPU           E3110  @ 3.00GHz Ge
nuineIntel GNU/Linux
$gcc -v
Reading specs from /usr/lib/gcc/i486-slackware-linux/4.5.2/specs
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/i486-slackware-linux/4.5.2/lto-wrapper
Target: i486-slackware-linux
Configured with: ../gcc-4.5.2/configure --prefix=/usr --libdir=/usr/lib --mandir=/usr/man --infodir=/usr/info --enable-
shared --enable-bootstrap --enable-languages=ada,c,c++,fortran,java,objc,lto --enable-threads=posix --enable-checking=r
elease --with-system-zlib --with-python-dir=/lib/python2.6/site-packages --disable-libunwind-exceptions --enable-__cxa_
atexit --enable-libssp --enable-lto --with-gnu-ld --verbose --with-arch=i486 --target=i486-slackware-linux --build=i486
-slackware-linux --host=i486-slackware-linux
Thread model: posix
gcc version 4.5.2 (GCC)

server.c：

#include <stdio.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/types.h>
#include <unistd.h>
#include <string.h>

int connection_handler(int connection_fd)
{
 int nbytes;
 char buffer[256];

 nbytes = read(connection_fd,buffer,256);
 buffer[nbytes] = 0;

 printf("MESSAGE FROM CLIENT: %sn",buffer);
 nbytes = snprintf(buffer,256,"hello from the server");
 write(connection_fd,nbytes);

 close(connection_fd);
 return 0;
}

int main(void)
{
 struct sockaddr_un address;
 int socket_fd,connection_fd;
 socklen_t address_length;
 pid_t child;

 socket_fd = socket(PF_UNIX,SOCK_STREAM,0);
 if(socket_fd < 0)
 {
  printf("socket() failedn");
  return 1;
 } 

 unlink("./demo_socket");

 /* start with a clean address structure */
 memset(&address,sizeof(struct sockaddr_un));

 address.sun_family = AF_UNIX;
 snprintf(address.sun_path,UNIX_PATH_MAX,"./demo_socket");

 if(bind(socket_fd,(struct sockaddr *) &address,sizeof(struct sockaddr_un)) != 0)
 {
  printf("bind() failedn");
  return 1;
 }

 if(listen(socket_fd,5) != 0)
 {
  printf("listen() failedn");
  return 1;
 }

 while((connection_fd = accept(socket_fd,&address_length)) > -1)
 {
  child = fork();
  if(child == 0)
  {
   /* now inside newly created connection handling process */
   return connection_handler(connection_fd);
  }

  /* still inside server process */
  close(connection_fd);
 }

 close(socket_fd);
 unlink("./demo_socket");
 return 0;
}

client.c：

#include <stdio.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <string.h>

int main(void)
{
 struct sockaddr_un address;
 int  socket_fd,nbytes;
 char buffer[256];

 socket_fd = socket(PF_UNIX,0);
 if(socket_fd < 0)
 {
  printf("socket() failedn");
  return 1;
 }

 /* start with a clean address structure */
 memset(&address,"./demo_socket");

 if(connect(socket_fd,sizeof(struct sockaddr_un)) != 0)
 {
  printf("connect() failedn");
  return 1;
 }

 nbytes = snprintf(buffer,"hello from a client");
 write(socket_fd,nbytes);

 nbytes = read(socket_fd,256);
 buffer[nbytes] = 0;

 printf("MESSAGE FROM SERVER: %sn",buffer);

 close(socket_fd);

 return 0;
}