该程序是一个虽然简单但是完整的tcp客户端/服务端实例。实现了本机客户与本机服务器的连接建立及相互发送消息。建立连接之后，客户端接收并打印出服务器发送来的数据。服务器打印出客户端的IP地址并向客户端发送数据。
服务器程序srv.c如下：
#include<stdio.h> #include<strings.h> #include<unistd.h> #include<arpa/inet.h> #include<sys/types.h> #include<sys/socket.h> #include<netinet/in.h> #define PORT 1234 #define BACKLOG 1 int main() { int listenfd,connectfd; struct sockaddr_in server; struct sockaddr_in client; int sin_size; if((listenfd=(socket(AF_INET,SOCK_STREAM,0)))==-1) { //handle exception perror("Creating socket failed"); exit(1); } bzero(&server,sizeof(server)); server.sin_family=AF_INET; server.sin_port=htons(PORT); server.sin_addr.s_addr=htonl(INADDR_ANY); /*Bind socket to address*/ if(bind(listenfd,(struct sockaddr *)&server,sizeof(struct sockaddr))==-1) { perror("Bind error"); exit(1); } /*Listen client's reqirement*/ if(listen(listenfd,BACKLOG)==-1) { perror("listen failed"); exit(1); } sin_size=sizeof(struct sockaddr_in); if((connectfd=accept(listenfd,(struct sockaddr *)&client,&sin_size))==-1) { perror("accept() error"); exit(1); } //prints client's IP printf("You got a connection from %s\n",inet_ntoa(client.sin_addr)); send(connectfd,"Welcome to my server.\n",22,0); close(connectfd); close(listenfd); }客户端程序cli.c如下：
#include<stdio.h> #include<unistd.h> #include<strings.h> #include<sys/types.h> #include<sys/socket.h> #include<netinet/in.h> #include<netdb.h> #define PORT 1234 #define MAXDATASIZE 100 int main(int argc,char *argv[]) { int fd,numbytes; char buf[MAXDATASIZE]; struct hostent *he; struct sockaddr_in server; if(argc!=2) { printf("Usage:%s<IP Address>",argv[0]); exit(1); } if((he=gethostbyname(argv[1]))==NULL) { perror("gethostbyname() error\n"); exit(1); } if((fd=(socket(AF_INET,SOCK_STREAM,0)))==-1) { printf("socket() error"); exit(1); } bzero(&server,sizeof(server)); server.sin_family=AF_INET; server.sin_port=htons(PORT); server.sin_addr=*((struct in_addr*)he->h_addr); /*Connect to server and receive data from the server.*/ if(connect(fd,(struct sockaddr *)&server,sizeof(struct sockaddr))==-1) { printf("connect() error\n"); exit(1); } if((numbytes=recv(fd,buf,MAXDATASIZE,0))==-1) { printf("recv() error"); exit(1); } buf[numbytes]='\0'; printf("Server Message: %s\n",buf); close(fd); }编译之后，首先启动服务器程序：
[root@mylinux 20160910]# ./srv再启动客户端程序：
[root@mylinux 20160910]# ./cli 127.0.0.1
服务器的运行结果：
[root@mylinux 20160910]# ./srv You got a connection from 127.0.0.1客户端的运行结果：
[root@mylinux 20160910]# ./cli 127.0.0.1 Server Message: Welcome to my server.
