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(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;
}

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(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;
}

  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 = 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");

　　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(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;
}