運用dup2的tcp socket通信

dup 和 dup2既然有重定向的功能，那麼我們之前寫的tcp socket通信是不是可以修改一下呢？比如，不用write往socket裏面寫，而直接用dup2/dup重定向呢？

答案是肯定的。

代碼如下

tcp_dup2_server

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

int startup(const char* _ip, int _port)
{
	int sock = socket(AF_INET, SOCK_STREAM, 0);
	if(sock < 0)
	{
		perror("socket");
		exit(2);
	}

	// bind綁定
	struct sockaddr_in local;
	local.sin_family = AF_INET;
	local.sin_port = htons(_port);
	local.sin_addr.s_addr = inet_addr(_ip);

	if(bind(sock, (struct sockaddr*)&local, sizeof(local)) < 0)
	{
		perror("bind---");
		exit(3);
	}

	if(listen(sock, 10) < 0)
	{
		perror("listen");
		exit(4);
	}
	return sock;
}


static void usage(const char *proc)
{
	printf("%s[ip][port]\n", proc);
}

int main(int argc, char *argv[])
{
	if(argc != 3)
	{
		usage(argv[0]);
		return 1;
	}

	//int sock =startup(argv[1], atoi(argv[2]));
	int listen_sock =startup(argv[1], atoi(argv[2]));
	struct sockaddr_in remote;
	socklen_t len = sizeof(remote);
	char buf[1024];
	sleep(2);
	while(1)
	{
		int sock = accept(listen_sock, (struct sockaddr*)&remote, &len);
		if(sock < 0)
		{
			perror("accept***************");
			continue;
		}
		printf("client ip: %s, port: %d\n", inet_ntoa(remote.sin_addr), ntohs(remote.sin_port));

		while(1)
		{
			ssize_t s = read(sock, buf, sizeof(buf)-1);
			if(s > 0)
			{
				buf[s] = 0;
				printf("client say# %s\n", buf);
				write(sock, buf, strlen(buf));	
			}else if(s == 0)
			{
				printf("client is lose");
				break;
			}
		}
	}
}

tcp_dup2_client

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

static void usage(const char *proc)
{
	printf("%s[ip][port]\n", proc);
}

int main(int argc, char *argv[])
{
	if(argc != 3)
	{
		usage(argv[0]);
		return 1;
	}

	int sock = socket(AF_INET, SOCK_STREAM, 0);
	if(sock < 0)
	{
		perror("socket");
		return 1;
	}

	struct sockaddr_in peer;
	peer.sin_family = AF_INET;
	peer.sin_port = htons(atoi(argv[2]));
	peer.sin_addr.s_addr = inet_addr(argv[1]);

	if(connect(sock, (struct sockaddr*)& peer, sizeof(peer)) < 0)
	{
		perror("connet");
		return 3;
	}

	char buf[1024];
	int ret = dup2(sock, 1);

	while(1)
	{
	//	printf("please user enter:");
	//	fflush(stdout);
		ssize_t _s = read(0, buf, sizeof(buf)-1);	
		
		if(_s > 0)
		{
			buf[_s-1] = 0;
			//write(sock, buf, sizeof(buf)-1);
		}

		printf("%s", buf);
		fflush(stdout);
	}
	close(sock);
}