C的SOCKET通讯的小例子

首先是服务器端的代码：（比较简单）

#include <stdio.h>
#include <sys/socket.h>
#include <unistd.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <time.h>

#define SERVER_PORT 20000 // define the defualt connect port id
#define LENGTH_OF_LISTEN_QUEUE 10 // length of listen queue in server
#define BUFFER_SIZE 255
#define WELCOME_MESSAGE "welcome to connect the server. "

int main(int argc, char** argv)
{
       int servfd,clifd;
       struct sockaddr_in servaddr,cliaddr;

       if ((servfd = socket(AF_INET,SOCK_STREAM, 0 )) < 0 )
         {
              printf( " create socket error!\n " );
              exit( 1 );
       }

       bzero( & servaddr, sizeof (servaddr));

       servaddr.sin_family = AF_INET;
       servaddr.sin_port = htons(SERVER_PORT);
       servaddr.sin_addr.s_addr = htons(INADDR_ANY);

       if (bind(servfd,( struct sockaddr * ) & servaddr, sizeof (servaddr)) < 0 )
         {
              printf( " bind to port %d failure!\n " ,SERVER_PORT);
              exit( 1 );
       }

        if (listen(servfd,LENGTH_OF_LISTEN_QUEUE) < 0 )
         {
              printf( " call listen failure!\n " );
              exit( 1 );
       }

        while ( 1 )
         { // server loop will nerver exit unless any body kill the process

              char buf[BUFFER_SIZE];
              long timestamp;
              socklen_t length = sizeof (cliaddr);
              clifd = accept(servfd,( struct sockaddr * ) & cliaddr, & length);

               if (clifd < 0 )
                {
                     printf( " error comes when call accept!\n " );
                     break ;
              }

              strcpy(buf,WELCOME_MESSAGE);

               // inet_ntop(INET_ADDRSTRLEN,cliaddr.sin_addr,buf,BUFFER_SIZE);

              printf( " from client,IP:%s,Port:%d\n " ,inet_ntoa(cliaddr.sin_addr),ntohs(cliaddr.sin_port));

              timestamp = time(NULL);

              strcat(buf, " timestamp in server: " );
              strcat(buf,ctime( & timestamp));

              send(clifd,buf,BUFFER_SIZE, 0 );

              close(clifd);

       } // exit

       close(servfd);

        return 0 ;
}

然后是客服端的代码：

#include <stdio.h>
#include <sys/socket.h>
#include <unistd.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <stdlib.h>


#define SERVER_PORT 20000 // define the defualt connect port id
#define CLIENT_PORT ((20001+rand())%65536) // define the defualt client port as a random port
#define BUFFER_SIZE 255
#define REUQEST_MESSAGE "welcome to connect the server.\n"


void usage(char* name)
{
       printf( " usage: %s IpAddr\n " ,name);
}


int main(int argc, char** argv)
{
       int servfd,clifd,length = 0;
       struct sockaddr_in servaddr,cliaddr;
       socklen_t socklen = sizeof (servaddr);
       char buf[BUFFER_SIZE];

        if (argc < 2 )
         {
              usage(argv[ 0 ]);
              exit( 1 );
       }

       if ((clifd = socket(AF_INET,SOCK_STREAM, 0 )) < 0 )
         {
             printf( " create socket error!\n " );
             exit( 1 );
       }

       srand(time(NULL)); // initialize random generator

       bzero( & cliaddr, sizeof (cliaddr));
       cliaddr.sin_family = AF_INET;
       cliaddr.sin_port = htons(CLIENT_PORT);
       cliaddr.sin_addr.s_addr = htons(INADDR_ANY);

       bzero( & servaddr, sizeof (servaddr));
       servaddr.sin_family = AF_INET;
       inet_aton(argv[ 1 ], & servaddr.sin_addr);
       servaddr.sin_port = htons(SERVER_PORT);
      // servaddr.sin_addr.s_addr = htons(INADDR_ANY);

       if (bind(clifd, (struct sockaddr* ) &cliaddr, sizeof (cliaddr)) < 0 )
       {
              printf( " bind to port %d failure!\n " ,CLIENT_PORT);
              exit( 1 );
       }

        if (connect(clifd,( struct sockaddr * ) & servaddr, socklen) < 0 )
       {
              printf( " can't connect to %s!\n ", argv[ 1 ]);
              exit( 1 );
       }

       length = recv(clifd, buf, BUFFER_SIZE, 0);
        if (length < 0)
        {
              printf( " error comes when recieve data from server %s! ", argv[1] );
              exit( 1 );
       }

       printf( " from server %s :\n\t%s", argv[1], buf);

       close(clifd);
       return 0;
}

以上只是作为一个小例子的SOCKET通讯代码。