LINUX网络编程之套接字

套接字可以让LINUX在网络上通信，用起来就像管道一样，当然管道都是单向的，套接字既能写也能收！

以下是多客户服务器代码：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <signal.h>
#include <arpa/inet.h>
#include <string.h>
#define PORT 6000
#define SIZE 256

static void handler()//回收子进程函数
{
	wait(NULL);
}

int main(int argc, char **argv)
{
	int server_socketfd;
	int client_socketfd;
	int ret;
	pid_t pid;
	size_t address_len;
	struct sockaddr_in server_address;
	struct sockaddr_in client_address;
	
	server_socketfd = socket(AF_INET, SOCK_STREAM,0);//创建一个套接字
	
	memset(&server_address,0,sizeof(struct sockaddr_in));
	
	server_address.sin_family = AF_INET;//协议族设置为ARPA因特网协议
	server_address.sin_port = htons(PORT);//端口号设为PORT（6000）
	server_address.sin_addr.s_addr = htonl(INADDR_ANY);//允许任何客户端可以连接
	address_len = sizeof(struct sockaddr_in);

	ret = bind(server_socketfd, (struct sockaddr*)&server_address, address_len);//将创建的套接字和address中的地址绑定在一起
	if( ret == -1 )
	{
		printf("bind failed!\n");
		exit(0);
	}
	
	ret = listen(server_socketfd, 5);//创建一个监听5个请求的队列，也就是说这个服务器允许5个人同时登入
	if ( ret == -1 )
	{
		printf("listen failed!\n");
		exit(0);
	}
	
	while (1)
	{
		client_socketfd = accept(server_socketfd, (struct sockaddr*)&client_address, &address_len);//客户连接服务器时建立客户套接字

		signal(SIGCHLD,handler);//为了避免子进程结束时造成僵尸进程，需要对结束子进程作处理，handler函数负责回收子进程

		pid = fork();
		if (pid == 0)//为客户分配的子进程
		{
			char buffer[256];
			int nread;
			nread = read(client_socketfd,buffer,sizeof(buffer));
			printf("%s",buffer);
				
		}
		else if (pid > 0)//父进程把分配的客户套接字关闭，用来供给下个客户
		{
			close(client_socketfd);//关闭客户套接字
		}
		else
		{
			printf("fork faild!\n");
			exit(0);
		}
	}
	return 0;
}

客户端代码：

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

#define SIZE 256
#define PORT 6000

int main()
{
	int socketfd;
	int ret;
	char buffer[SIZE];
	struct sockaddr_in address;

	socketfd = socket(AF_INET, SOCK_STREAM, 0);//创建一个套接字

	address.sin_family = AF_INET;//设置为因特网协议
	address.sin_port = htons(PORT);//设置端口号
	inet_pton(AF_INET, "127.0.0.1", &address.sin_addr.s_addr);//设置ip地址

	ret = connect(socketfd, (struct sockaddr*) &address, sizeof(address));//连接服务器

	if (ret == -1)
	{
		printf("can't connect!\n");
		exit(0);
	}
		
	printf("send:");
	fgets(buffer,sizeof(buffer),stdin);
	write(socketfd,buffer,sizeof(buffer));//把数据传给服务器

	close(socketfd);//关闭套接字
	return 0;
}