Linux Socket编程实例(一个Hello World程序)

在Linux下写了个小的 socket程序，分为客户端和服务器端,服务端开一个端口(2000),做为一个daemon,等待客户的连接请求.一旦有客户连接,服务器端打印出客户端的IP地址和端口,并且向服务器端发送欢迎信息和时间.下面是服务端的代码(tcpserver.c).由于这只是个简单的程序，所以只用了单线程实现!

/**

* Tcp Server program, It is a simple example only.

* zhengsh 200520602061 2

* when client connect to server, send a welcome message and timestamp in server.

*/



#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(×tamp));

              send(clifd,buf,BUFFER_SIZE,0);

              close(clifd);         

           

      }//exit

       close(servfd);

       return 0;

}



客户每次用一个随机的端口连接服务器,并接收来自服务器的欢迎信息

,然后打印出来(tcpclient).运行的时候接受一个参数,也就是服务器的ip地址.

/* Tcp client program, It is a simple example only.

* zhengsh 200520602061 2

* connect to server, and echo a message from server.

*/





#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;

}

程序在Fedora core 4下通过编译,有几个warining.但是不影响.