socket编程与利用进程进行多并行连接

呈现一张基本的socket阻塞式模型，如下图：

　　　　　　　　　　　　　　　　　　　　

　一：　对于一对一的进行C/S回射：

服务端（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();    \
      }while()

 int
 main (void)
 {
   int sock, conn;
   if ((sock = socket (PF_INET, SOCK_STREAM, )) < )
     ERR_EXIT ("socket");
   struct sockaddr_in sockaddr;
   memset (&sockaddr, , sizeof (sockaddr));
   sockaddr.sin_family = AF_INET;
   sockaddr.sin_port = htons ();
   sockaddr.sin_addr.s_addr = htonl (INADDR_ANY);
   if (bind (sock, (struct sockaddr *) &sockaddr, sizeof (sockaddr)) < )
     ERR_EXIT ("Bind");
   if (listen (sock, SOMAXCONN) < )
     ERR_EXIT ("Listen");
   struct sockaddr_in client;
   memset (&client, , sizeof (client));
   socklen_t addrlen = sizeof (client);
   if ((conn = accept (sock, (struct sockaddr *) &client, &addrlen)) < )
     ERR_EXIT ("Accept");
   char sed[], recv[];
   while (fgets (sed, sizeof (sed), stdin) != NULL ||  == )
     {
       if (strlen (sed) > )
         write (conn, sed, sizeof (sed));
       if (read (conn, recv, sizeof (recv)) > )
         {
           fputs (recv, stdout);
           if (strcmp (recv, "exit") == )
             break;
           write (conn, recv, sizeof (recv));
         }
       else
         ERR_EXIT ("read...");
     }
   close (conn);
   close (sock);
   return ;
 }

客户端（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();       \
     }while();

 int
 main (void)
 {
   int socketid, conn;

   if ((socketid = socket (PF_INET, SOCK_STREAM, IPPROTO_TCP)) < )
     ERR_EXIT ("socket");

   struct sockaddr_in server_addr;
   memset (&server_addr, , sizeof (server_addr));

   server_addr.sin_family = AF_INET;
   server_addr.sin_port = htons ();
   server_addr.sin_addr.s_addr = inet_addr ("127.0.0.1");
   if ((conn =
        connect (socketid, (struct sockaddr *) &server_addr,
                 sizeof (server_addr))) < )
     ERR_EXIT ("connect");
   char sendbuf[], recivebuf[];
   while (fgets (sendbuf, sizeof (sendbuf), stdin) != NULL)
     {
       write (socketid, sendbuf, sizeof (sendbuf));
       read (socketid, recivebuf, sizeof (recivebuf));
       fputs (recivebuf, stdout);
       if (strcmp (recivebuf, "exit") == )
         {
           ERR_EXIT ("exit");
           break;
         }
     }
   close (conn);
   close (socketid);
   return ;
 }

相关的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)

但是上述虽然满足了基本的socket套路，但是当我们关闭服务可执行程序时，在开启就会出现地址被占用，解决此等问题，需再加上一个setsockopt()函数，对齐进行设定。

详细可以去查询man帮助（man  setsockopt）

代码：

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

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

　　二：  利用进程进行并行socket阻塞式连接：

        客户端和makefile文件和上面一样，只是将socket的服务端，修改为调用进程来进行多并发连接即可！

服务端（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();    \
      }while()

 void
 print (int conn){

   char sed[], recv[];
   while (fgets (sed, sizeof (sed), stdin) != NULL ||  == )
     {
       if (strlen (sed) > )
          write (conn, sed, sizeof (sed));
       if (read (conn, recv, sizeof (recv)) > )
         {
           fputs (recv, stdout);
           if (strcmp (recv, "exit") == )
                     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, )) < )
     ERR_EXIT ("socket");
   struct sockaddr_in sockaddr;
   memset (&sockaddr, , sizeof (sockaddr));
   sockaddr.sin_family = AF_INET;
   sockaddr.sin_port = htons ();
   sockaddr.sin_addr.s_addr = htonl (INADDR_ANY);

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

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

   if (listen (sock, SOMAXCONN) < )
     ERR_EXIT ("Listen");

   struct sockaddr_in client;
   memset (&client, , sizeof (client));
   socklen_t addrlen = sizeof (client);
   pid_t pid ;

   while ()
     {
    if((conn = accept (sock, (struct sockaddr *) &client, &addrlen)) < )
         ERR_EXIT ("Accept");
           pid = fork ();
       if (pid == -)
            ERR_EXIT ("fork");
       else if (pid == ){
            close (sock);
            print (conn);
         }
       else
         close (conn);
     }
   close (sock);
   return ;
 }