Linux Socket编程实例(一个Hello World程序)

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(&timestamp));
              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.