呈現一張基本的socket阻塞式模型，如下圖：

一：　對于一對一的進行C/S回射：

服務端（server.c）：

#include<unistd.h>

include<stdio.h>
include<string.h>
include<stdlib.h>
include<netinet/in.h>
include<sys/socket.h>
include<sys/types.h>
include<error.h>
define ERR_EXIT(m) \
do{           \
      perror(m); \
      exit(1);    \
     }while(0)
int
main (void)
{
  int sock, conn;
  if ((sock = socket (PF_INET, SOCK_STREAM, 0)) < 0)
    ERR_EXIT ("socket");
  struct sockaddr_in sockaddr;
  memset (&sockaddr, 0, sizeof (sockaddr));
  sockaddr.sin_family = AF_INET;
  sockaddr.sin_port = htons (5528);
  sockaddr.sin_addr.s_addr = htonl (INADDR_ANY);
  if (bind (sock, (struct sockaddr ) &sockaddr, sizeof (sockaddr)) < 0)
    ERR_EXIT ("Bind");
  if (listen (sock, SOMAXCONN) < 0)
    ERR_EXIT ("Listen");
  struct sockaddr_in client;
  memset (&client, 0, sizeof (client));
  socklen_t addrlen = sizeof (client);
  if ((conn = accept (sock, (struct sockaddr ) &client, &addrlen)) < 0)
    ERR_EXIT ("Accept");
  char sed[1024], recv[1024];
  while (fgets (sed, sizeof (sed), stdin) != NULL || 1 == 1)
    {
      if (strlen (sed) > 0)
        write (conn, sed, sizeof (sed));
      if (read (conn, recv, sizeof (recv)) > 0)
        {
          fputs (recv, stdout);
          if (strcmp (recv, "exit") == 0)
            break;
          write (conn, recv, sizeof (recv));
        }
      else
        ERR_EXIT ("read...");
    }
  close (conn);
  close (sock);
  return 0;
}</pre>

客戶端（client.c）： 
#include<unistd.h>

include<stdio.h>
include<string.h>
include<error.h>
include<netinet/in.h>
include<stdlib.h>
include<sys/socket.h>
include<sys/types.h>
define ERR_EXIT( m ) \
do{          \
      perror(m);   \
      exit(1);       \
    }while(0);
int
main (void)
{
  int socketid, conn;
if ((socketid = socket (PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
    ERR_EXIT ("socket");
struct sockaddr_in server_addr;
  memset (&server_addr, 0, sizeof (server_addr));
server_addr.sin_family = AF_INET;
  server_addr.sin_port = htons (5528);
  server_addr.sin_addr.s_addr = inet_addr ("127.0.0.1");
  if ((conn =
       connect (socketid, (struct sockaddr *) &server_addr,
                sizeof (server_addr))) < 0)
    ERR_EXIT ("connect");
  char sendbuf[1024], recivebuf[1024];
  while (fgets (sendbuf, sizeof (sendbuf), stdin) != NULL)
    {
      write (socketid, sendbuf, sizeof (sendbuf));
      read (socketid, recivebuf, sizeof (recivebuf));
      fputs (recivebuf, stdout);
      if (strcmp (recivebuf, "exit") == 0)
        {
          ERR_EXIT ("exit");
          break;
        }
    }
  close (conn);
  close (socketid);
  return 0;
}</pre>

  相關的makefile文件 

makefile文件：

.SUFFIXES: .o.c
.PHONY: clean
.PHONY: start
CC =gcc
SRC =server.c
OBJS =$(SRC:.c =.o)
BIN = Server
start:
        $(CC) -o $(BIN) $(OBJS)
.o.c:
        $(CC) -g -Wall $@ -c $<
clean:
        rm -f $(OBJS)</pre>

但是上述雖然滿足了基本的socket套路，但是當我們關閉服務可執行程序時，在開啟就會出現地址被占用，解決此等問題，需再加上一個setsockopt()函數，對齊進行設定。 

詳細可以去查詢man幫助（man  setsockopt） 

   代碼：

         

int on = 1;
  if (setsockopt (sock, SOL_SOCKET, SO_REUSEADDR, &on, sizeof (on)) < 0)
    {
      ERR_EXIT ("setsockopt");
    }

if (bind (sock, (struct sockaddr *) &sockaddr, sizeof (sockaddr)) < 0)
    ERR_EXIT ("Bind");</pre>

二：  利用進程進行并行socket阻塞式連接： 
        客戶端和makefile文件和上面一樣，只是將socket的服務端，修改為調用進程來進行多并發連接即可！ 

  

      服務端（server.c）： 

#include<unistd.h>

include<stdio.h>
include<string.h>
include<stdlib.h>
include<netinet/in.h>
include<sys/socket.h>
include<sys/types.h>
include<error.h>
define ERR_EXIT(m) \
do{           \
      perror(m); \
      exit(1);    \
     }while(0)
void
print (int conn){
char sed[1024], recv[1024];
  while (fgets (sed, sizeof (sed), stdin) != NULL || 1 == 1)
    {
      if (strlen (sed) > 0)
         write (conn, sed, sizeof (sed));
      if (read (conn, recv, sizeof (recv)) > 0)
        {
          fputs (recv, stdout);
          if (strcmp (recv, "exit") == 0)
                    break;
          write (conn, recv, sizeof (recv));
        }
      else
        ERR_EXIT ("read...");
   }
    close (conn);
}
int
main (void)
{
  int sock, conn;
  if ((sock = socket (PF_INET, SOCK_STREAM, 0)) < 0)
    ERR_EXIT ("socket");
  struct sockaddr_in sockaddr;
  memset (&sockaddr, 0, sizeof (sockaddr));
  sockaddr.sin_family = AF_INET;
  sockaddr.sin_port = htons (5528);
  sockaddr.sin_addr.s_addr = htonl (INADDR_ANY);
int on = 1;
  if (setsockopt (sock, SOL_SOCKET, SO_REUSEADDR, &on, sizeof (on)) < 0)
    {
      ERR_EXIT ("setsockopt");
    }
if (bind (sock, (struct sockaddr *) &sockaddr, sizeof (sockaddr)) < 0)
    ERR_EXIT ("Bind");
if (listen (sock, SOMAXCONN) < 0)
    ERR_EXIT ("Listen");
struct sockaddr_in client;
  memset (&client, 0, sizeof (client));
  socklen_t addrlen = sizeof (client);
  pid_t pid ;
while (1)
    {
   if((conn = accept (sock, (struct sockaddr *) &client, &addrlen)) < 0)
        ERR_EXIT ("Accept");
          pid = fork ();
      if (pid == -1)
           ERR_EXIT ("fork");
      else if (pid == 0){
           close (sock);
           print (conn);
        }
      else
        close (conn);
    }
  close (sock);
  return 0;
}</pre>

編程是一種快樂，享受代碼帶給我的樂趣！！！


來自：http://www.cnblogs.com/gongxijun/p/4592864.html