C语言socket入门

socket协议

三次握手与结束连接

客户端代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h> //for bzero

#include <netinet/in.h> //for socketaddr_in
#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>

#define PORT 5050    //端口号
#define MAXLEN_FOR_DATA  1024//数据的最大长度

int main(){
	
	int clientfd;// 套接字
	int len, ret;
	char buf[MAXLEN_FOR_DATA];	
	
	struct sockaddr_in serveraddr;
	
	//建立套接口
	clientfd = socket(AF_INET, SOCK_STREAM, 0);
	if (clientfd == -1){
		fprintf(stderr, "Failed: socket()\n ");
		goto exit;	
	}
	printf("Sucessed: socket()\n");
	
	
	//****连接********
	serveraddr.sin_family = AF_INET;
	serveraddr.sin_addr.s_addr = inet_addr("127.0.0.1");
	serveraddr.sin_port = htons(PORT);
	len = sizeof(serveraddr);
	ret =  connect(clientfd, (struct sockaddr*)&serveraddr, len);
	if (ret == -1){
		fprintf(stderr, "Failed: connect()\n");
		goto exit;
	}
	printf("Sucessed: connect() \n");
	
	sprintf(buf, "%s \n", "Hello World!");
	ret = send(clientfd, (void*)buf, strlen(buf), 0);
	if (ret <= 0){
		fprintf(stderr, "Failed: send()\n");
		goto exit;
	}
	printf("Sucessed: send()\n");
	
	
	exit:
		close(clientfd);
		clientfd = -1;
		return 0;
}

服务器：

#include <stdio.h>
#include <stdlib.h>
#include <string.h> //for bzero

#include <netinet/in.h> //for socketaddr_in
#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>

#define PORT 5050
#define LEN_FOR_LISTEN_QUEUE 5
#define MAXLEN_FOR_DATA 1024

int main(){
	
	//
	int serverfd, clientfd;//套接字
	int len;
	int ret;
	char buf[MAXLEN_FOR_DATA];
	struct sockaddr_in serveraddr;//服务器地址信息
	struct sockaddr_in clientaddr;
	
	
	//创建套接口
	serverfd = socket(AF_INET, SOCK_STREAM, 0);
	if (serverfd == -1){
		fprintf(stderr, "Failed: socket()\n");
		goto exit;
	}
	printf("Sucessed: socket()\n");
	
	
	//绑定地址和端口号
	serveraddr.sin_family = AF_INET;
	serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);
	serveraddr.sin_port = htons(PORT);
	len = sizeof(serveraddr);
	ret = bind(serverfd, (struct sockaddr*)&serveraddr, len);
	if (ret == -1){
		fprintf(stderr, "Failed: bind()\n");
		goto exit;	
	}
	printf("Sucessed:bind()\n");
	
	//建立套接口监听队列
	ret = listen(serverfd, LEN_FOR_LISTEN_QUEUE);
	if (ret == -1){
		fprintf(stderr, "Failed: listen()\n");
		goto exit;	
	}
	printf("Sucess:listen()\n");
	
	while (1){
		printf("Wait For..\n");
		fflush(stdout);
		
		
		//接受连接
		len = sizeof(clientaddr);
		clientfd = accept(serverfd, (struct sockaddr*)&clientaddr, &len);
		if (clientfd == -1){
			fprintf(stderr, "Failed: accept()\n");
			goto exit;	
		}
		printf("Sucessed:accept()!\n");
		
		
		//接受数据
		ret = recv(clientfd, (void*)buf, MAXLEN_FOR_DATA, 0);
		if (ret <= 0){
			fprintf(stderr, "Failed: recv()\n");	
		}
		else {
			printf("Sucessed: recv()\n Data:%s", buf);	
		}
		
		
		//关闭连接
		close(clientfd);
		printf("Closed!\n");
	}
	
	exit:
		return 0;
}