Linux下的socket網絡編程（1）

   模仿服務器端與客戶端之間的通信：

   服務器端實現多進程返回客戶端的輸入信息的功能。

   客戶端實現數據的寫入傳輸了打印。

   服務器端：

#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

#define  ERR_EXIT(m)\  //宏定義
		do \
		{\
			perror(m); \
			exit(EXIT_FAILURE); \
		} while(0)
void do_service(int conn)  //返回客戶端數據
{
	char recvbuff[1024];
	while(1)
	{
		memset(recvbuff, 0, sizeof(recvbuff));
		int ret = read(conn, recvbuff, sizeof(recvbuff));
		if(ret == 0)
		{
			printf("client_close\n");
			break;
		}
		else if(ret == -1)
			ERR_EXIT("read");
		fputs(recvbuff, stdout);
		write(conn, recvbuff, ret);
	}
}
int main(void)
{
	int listenfd;
	if((listenfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) //創建一個socket
	/*if((listenfd = socket(AF_INET, SOCKET_STREAM, 0)) < 0)*/
		ERR_EXIT("socket");

	struct sockaddr_in servaddr;
	memset(&servaddr, 0, sizeof(servaddr));         //初始化sockaddr_in(IP地址及端口)
	servaddr.sin_family = AF_INET;
	servaddr.sin_port = htons(8080);
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	/*servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");*/
	/*inet_aton("127.0.0.1", &servaddr.sin_addr);*/
	
	int on = 1;                                                               
	if(setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)//使用REUSEADDR使得端口立即關閉 
		ERR_EXIT("setsockopt");
	
	if(bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0) //綁定socket
		ERR_EXIT("bind"); 
	
	if(listen(listenfd, SOMAXCONN) < 0) //監聽socket，程序阻塞等待連接
		ERR_EXIT("listen");

	struct sockaddr_in perraddr; //初始化連接的socket
	socklen_t peerlen = sizeof(perraddr);
	int conn;
	
	pid_t pid;//使用fork()創建子進程，函數返回兩個參數，子進程pid = 0，父進程是pid = 子進程pid號
	while(1)
	{	
		if((conn = accept(listenfd, (struct sockaddr*)&perraddr, &peerlen)) < 0)<span style="font-family:KaiTi_GB2312;">//進行TCP三次握手</span>
			ERR_EXIT("accept");
		printf("ip=%s port=%d\n", inet_ntoa(perraddr.sin_addr), ntohs(perraddr.sin_port));
		pid = fork();
		if(pid == -1)
			ERR_EXIT("fork");
		if(pid == 0)
		{
			close(listenfd);
			do_service(conn);
			exit(EXIT_SUCCESS);
		}
		else
			close(conn);
	}
	return 0;	
}

   客戶端：

#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

#define  ERR_EXIT(m)\
		do \
		{\
			perror(m); \
			exit(EXIT_FAILURE); \
		} while(0)

int main(void)
{
	int sock;
	if((sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)  //初始化socket
	/*if((listenfd = socket(AF_INET, SOCKET_STREAM, 0)) < 0)*/
		ERR_EXIT("socket");
	struct sockaddr_in servaddr;  //初始化sockaddr_in
	memset(&servaddr, 0, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_port = htons(8080);
	servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");
	
	if(connect(sock, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0)  //連接客戶端，進行TCP三次握手
		ERR_EXIT("connect");
	char sendbuff[1024] = {0}; //初始化發送字符數組
	char recvbuff[1024] = {0}; //初始化接受字符數組
	while(fgets(sendbuff, sizeof(sendbuff), stdin) != NULL)
	{
		write(sock, sendbuff, strlen(sendbuff));
		read(sock, recvbuff, sizeof(recvbuff));
		fputs(recvbuff, stdout);
		memset(&recvbuff, 0, sizeof(recvbuff));
		memset(&sendbuff, 0, sizeof(sendbuff));
	}
	close(sock);
	return 0;	
}