TCP programming example
TCP programming is divided into two parts: client and server. The server first establishes a socket, then binds to the local port, then begins to receive the client's connection request and establishes a connection with it, and finally receives the message sent by the client ; The client calls the connect() function to establish a connection after the socket is established.
The process of using TCP on the server side and the client side is shown below:
Server side code:
/*****server.c*****/
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define BUFFER_SIZE 128
int main(int argc, char *argv[]){
int listenfd, connfd;
struct sockaddr_in servaddr, cliaddr;
socklen_t peerlen;
char[BUFFER_SIZE];
if(argc < 3){
printf("Usage: %s <ip> <port>\n",argv[0]);
exit(-1);
}
if((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
//建立socket连接
perror("socket");
exit(-1);
}
printf("listenfd = %d\n",listenfd);
//设置sockaddr_in结构体中相关参数
bzero(&servaddr,szieof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(atoi(argv[2]));
servaddr.sin_addr.s_addr = inet_addr(argv[1]);
if(bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) < 0){
//bind()绑定地址信息
perror("bind");
exit(-1);
}
printf("bind success!\n");
if(listen(listenfd, 10) == -1){
//listen()设置监听模式
perror("listen");
exit(-1);
}
printf("Listening...\n");
peerlen = sizeof(cliaddr); //调用accept()等待客户端的连接
while(1){
if((connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &peerlen)) <0){
perror("accept");
exit(-1);
}
memset(buf, 0, sizeof(buf)); //调用recv()函数接收客户端发送的数据
if(recv(connfd, buf, BUFFER_SIZE, 0) == -1){
perror("recv");
exit(-1);
}
printf("Received a message: %s\n",buf);
strcpy(buf, "Welcome to server");
send(connfd, buf, BUFFER_SIZE, 0);
close(connfd);
}
close(listenfd);
exit(0);
}
Client code:
/*****client.c*****/
//头文件同server.c
#define BUFFER_SIZE 128
int main(int argc, char *argv[]){
int sockfd;
char buf[BUFFER_SIZE] = "Hello Server";
struct sockaddr_in servaddr;
if(argc < 3){
printf("Usage: %s <ip> <port>\n",argv[0]);
exit(-1);
}
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
//创建socket
perror("socket");
exit(-1);
}
//设置sockaddr_in结构体中相关参数
bzero(&servaddr,szieof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(atoi(argv[2]));
servaddr.sin_addr.s_addr = inet_addr(argv[1]);
if(connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1){
perror("connect"); //调用connect()向服务器端建立TCP连接
exit(-1);
}
send(sockfd, buf, sizeof(buf), 0); //发送消息给服务器端
if(recv(sockfd, buf, sizeof(buf), 0) == -1){
perror("recv");
exit(-1);
}
printf("Recv from server: %s\n",buf);
close(sockfd);
exit(0);
}
When running, start the server first, then start the client
linux@linux-virtual-machine:~/andy/net$ ./server 192.168.1.100 9999
listenfd = 3
Bind success!
Listening...
Received a message: Hello Server
linux@linux-virtual-machine:~/andy/net$ ./client 192.168.1.100 9999
Recv from server: Welcome to server