├── client.c
├── server.c
├── 客户端说明.txt
├── 服务端说明.txt
└── 运行实例.txt


/client.c:
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  1 | /*文件：client.c
  2 | PS：第一个连接上服务器的客户端，称为client1，第二个连接上服务器的客户端称为client2
  3 | 这个程序的功能是：先连接上服务器，根据服务器的返回决定它是client1还是client2，
  4 | 若是client1，它就从服务器上得到client2的IP和Port，连接上client2,
  5 | 若是client2，它就从服务器上得到client1的IP和Port和自身经转换后的port，
  6 | 在尝试连接了一下client1后（这个操作会失败），然后根据服务器返回的port进行监听。
  7 | 这样以后，就能在两个客户端之间进行点对点通信了。
  8 | */
  9 | 
 10 | #include <stdio.h>
 11 | #include <unistd.h>
 12 | #include <signal.h>
 13 | #include <sys/socket.h>
 14 | #include <fcntl.h>
 15 | #include <stdlib.h>
 16 | #include <errno.h>
 17 | #include <string.h>
 18 | #include <arpa/inet.h>
 19 | 
 20 | #define MAXLINE 128
 21 | #define SERV_PORT 8877
 22 | 
 23 | typedef struct
 24 | {
 25 | 	char ip[32];
 26 | 	int port;
 27 | }server;
 28 | 
 29 | //发生了致命错误，退出程序
 30 | void error_quit(const char *str)    
 31 | {    
 32 | 	fprintf(stderr, "%s", str); 
 33 | 	//如果设置了错误号，就输入出错原因
 34 | 	if( errno != 0 )
 35 | 		fprintf(stderr, " : %s", strerror(errno));
 36 | 	printf("\n");
 37 | 	exit(1);    
 38 | }   
 39 | 
 40 | int main(int argc, char **argv)     
 41 | {          
 42 | 	int i, res, port;
 43 | 	int connfd, sockfd, listenfd; 
 44 | 	unsigned int value = 1;
 45 | 	char buffer[MAXLINE];      
 46 | 	socklen_t clilen;        
 47 | 	struct sockaddr_in servaddr, sockaddr, connaddr;  
 48 | 	server other;
 49 | 
 50 | 	if( argc != 2 )
 51 | 		error_quit("Using: ./client <IP Address>");
 52 | 
 53 | 	//创建用于链接（主服务器）的套接字        
 54 | 	sockfd = socket(AF_INET, SOCK_STREAM, 0); 
 55 | 	memset(&sockaddr, 0, sizeof(sockaddr));      
 56 | 	sockaddr.sin_family = AF_INET;      
 57 | 	sockaddr.sin_addr.s_addr = htonl(INADDR_ANY);      
 58 | 	sockaddr.sin_port = htons(SERV_PORT);      
 59 | 	inet_pton(AF_INET, argv[1], &sockaddr.sin_addr);
 60 | 	//设置端口可以被重用
 61 | 	setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &value, sizeof(value));
 62 | 
 63 | 	//连接主服务器
 64 | 	res = connect(sockfd, (struct sockaddr *)&sockaddr, sizeof(sockaddr)); 
 65 | 	if( res < 0 )
 66 | 		error_quit("connect error");
 67 | 
 68 | 	//从主服务器中读取出信息
 69 | 	res = read(sockfd, buffer, MAXLINE);
 70 | 	if( res < 0 )
 71 | 		error_quit("read error");
 72 | 	printf("Get: %s", buffer);
 73 | 
 74 | 	//若服务器返回的是first，则证明是第一个客户端
 75 | 	if( 'f' == buffer[0] )
 76 | 	{
 77 | 		//从服务器中读取第二个客户端的IP+port
 78 | 		res = read(sockfd, buffer, MAXLINE);
 79 | 		sscanf(buffer, "%s %d", other.ip, &other.port);
 80 | 		printf("ff: %s %d\n", other.ip, other.port);
 81 | 
 82 | 		//创建用于的套接字        
 83 | 		connfd = socket(AF_INET, SOCK_STREAM, 0); 
 84 | 		memset(&connaddr, 0, sizeof(connaddr));      
 85 | 		connaddr.sin_family = AF_INET;      
 86 | 		connaddr.sin_addr.s_addr = htonl(INADDR_ANY);      
 87 | 		connaddr.sin_port = htons(other.port);    
 88 | 		inet_pton(AF_INET, other.ip, &connaddr.sin_addr);
 89 | 
 90 | 		//尝试去连接第二个客户端，前几次可能会失败，因为穿透还没成功，
 91 | 		//如果连接10次都失败，就证明穿透失败了（可能是硬件不支持）
 92 | 		while( 1 )
 93 | 		{
 94 | 			static int j = 1;
 95 | 			res = connect(connfd, (struct sockaddr *)&connaddr, sizeof(connaddr)); 
 96 | 			if( res == -1 )
 97 | 			{
 98 | 				if( j >= 10 )
 99 | 					error_quit("can't connect to the other client\n");
100 | 				printf("connect error, try again. %d\n", j++);
101 | 				sleep(1);
102 | 			}
103 | 			else 
104 | 				break;
105 | 		}
106 | 
107 | 		strcpy(buffer, "Hello, world\n");
108 | 		//连接成功后，每隔一秒钟向对方（客户端2）发送一句hello, world
109 | 		while( 1 )
110 | 		{
111 | 			res = write(connfd, buffer, strlen(buffer)+1);
112 | 			if( res <= 0 )
113 | 				error_quit("write error");
114 | 			printf("send message: %s", buffer);
115 | 			sleep(1);
116 | 		}
117 | 	}
118 | 	//第二个客户端的行为
119 | 	else
120 | 	{
121 | 		//从主服务器返回的信息中取出客户端1的IP+port和自己公网映射后的port
122 | 		sscanf(buffer, "%s %d %d", other.ip, &other.port, &port);
123 | 
124 | 		//创建用于TCP协议的套接字        
125 | 		sockfd = socket(AF_INET, SOCK_STREAM, 0); 
126 | 		memset(&connaddr, 0, sizeof(connaddr));      
127 | 		connaddr.sin_family = AF_INET;      
128 | 		connaddr.sin_addr.s_addr = htonl(INADDR_ANY);      
129 | 		connaddr.sin_port = htons(other.port);      
130 | 		inet_pton(AF_INET, other.ip, &connaddr.sin_addr);
131 | 		//设置端口重用
132 | 		setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &value, sizeof(value));
133 | 
134 | 		//尝试连接客户端1，肯定会失败，但它会在路由器上留下记录，
135 | 		//以帮忙客户端1成功穿透，连接上自己 
136 | 		res = connect(sockfd, (struct sockaddr *)&connaddr, sizeof(connaddr)); 
137 | 		if( res < 0 )
138 | 			printf("connect error\n");
139 | 
140 | 		//创建用于监听的套接字        
141 | 		listenfd = socket(AF_INET, SOCK_STREAM, 0); 
142 | 		memset(&servaddr, 0, sizeof(servaddr));      
143 | 		servaddr.sin_family = AF_INET;      
144 | 		servaddr.sin_addr.s_addr = htonl(INADDR_ANY);      
145 | 		servaddr.sin_port = htons(port);
146 | 		//设置端口重用
147 | 		setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &value, sizeof(value));
148 | 
149 | 		//把socket和socket地址结构联系起来 
150 | 		res = bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr));    
151 | 		if( -1 == res )
152 | 			error_quit("bind error");
153 | 
154 | 		//开始监听端口       
155 | 		res = listen(listenfd, INADDR_ANY);    
156 | 		if( -1 == res )
157 | 			error_quit("listen error");
158 | 
159 | 		while( 1 )
160 | 		{
161 | 			//接收来自客户端1的连接
162 | 			connfd = accept(listenfd,(struct sockaddr *)&sockaddr, &clilen);  
163 | 			if( -1 == connfd )
164 | 				error_quit("accept error");
165 | 
166 | 			while( 1 )
167 | 			{
168 | 				//循环读取来自于客户端1的信息
169 | 				res = read(connfd, buffer, MAXLINE);
170 | 				if( res <= 0 )
171 | 					error_quit("read error");
172 | 				printf("recv message: %s", buffer);
173 | 			}
174 | 			close(connfd);
175 | 		}
176 | 	}
177 | 
178 | 	return 0;
179 | }
180 | 


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/server.c:
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https://raw.githubusercontent.com/weiyu666/Penetrate_NAT_TCP/4222566fd8dd6984047130f235b6768fdc07891e/server.c


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/客户端说明.txt:
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https://raw.githubusercontent.com/weiyu666/Penetrate_NAT_TCP/4222566fd8dd6984047130f235b6768fdc07891e/客户端说明.txt


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/服务端说明.txt:
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https://raw.githubusercontent.com/weiyu666/Penetrate_NAT_TCP/4222566fd8dd6984047130f235b6768fdc07891e/服务端说明.txt


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/运行实例.txt:
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https://raw.githubusercontent.com/weiyu666/Penetrate_NAT_TCP/4222566fd8dd6984047130f235b6768fdc07891e/运行实例.txt


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