我想通过一个带有静态 IP 的服务器来帮助两个客户端进行 UDP 穿透。服务器在端口7070和7071上等待两个客户端连接，并将各自的 IP 地址和端口发送给对方，这部分工作很好地完成了。但是我无法在两个客户端之间建立通信。我尝试在不同的WiFi网络和3G移动网络中运行代码，但是客户端程序会抛出“无法路由到主机”的 IO 异常。客户端代码用于两个客户端，一次使用端口7070，一次使用端口7071。
您认为我是否正确实现了 UDP 穿透概念？有什么想法可以让它正常工作吗？以下先展示服务器代码，然后是客户端代码。
感谢您的帮助。
服务器代码：
public class UDPHolePunchingServer {
public static void main(String args[]) throws Exception {
// Waiting for Connection of Client1 on Port 7070
// ////////////////////////////////////////////////
// open serverSocket on Port 7070
DatagramSocket serverSocket1 = new DatagramSocket(7070);
System.out.println("Waiting for Client 1 on Port "
+ serverSocket1.getLocalPort());
// receive Data
DatagramPacket receivePacket = new DatagramPacket(new byte[1024], 1024);
serverSocket1.receive(receivePacket);
// Get IP-Address and Port of Client1
InetAddress IPAddress1 = receivePacket.getAddress();
int port1 = receivePacket.getPort();
String msgInfoOfClient1 = IPAddress1 + "-" + port1 + "-";
System.out.println("Client1: " + msgInfoOfClient1);
// Waiting for Connection of Client2 on Port 7071
// ////////////////////////////////////////////////
// open serverSocket on Port 7071
DatagramSocket serverSocket2 = new DatagramSocket(7071);
System.out.println("Waiting for Client 2 on Port "
+ serverSocket2.getLocalPort());
// receive Data
receivePacket = new DatagramPacket(new byte[1024], 1024);
serverSocket2.receive(receivePacket);
// GetIP-Address and Port of Client1
InetAddress IPAddress2 = receivePacket.getAddress();
int port2 = receivePacket.getPort();
String msgInfoOfClient2 = IPAddress2 + "-" + port2 + "-";
System.out.println("Client2:" + msgInfoOfClient2);
// Send the Information to the other Client
// /////////////////////////////////////////////////
// Send Information of Client2 to Client1
serverSocket1.send(new DatagramPacket(msgInfoOfClient2.getBytes(),
msgInfoOfClient2.getBytes().length, IPAddress1, port1));
// Send Infos of Client1 to Client2
serverSocket2.send(new DatagramPacket(msgInfoOfClient1.getBytes(),
msgInfoOfClient1.getBytes().length, IPAddress2, port2));
//close Sockets
serverSocket1.close();
serverSocket2.close();
}
客户端代码
public class UDPHolePunchingClient {
public static void main(String[] args) throws Exception {
// prepare Socket
DatagramSocket clientSocket = new DatagramSocket();
// prepare Data
byte[] sendData = "Hello".getBytes();
// send Data to Server with fix IP (X.X.X.X)
// Client1 uses port 7070, Client2 uses port 7071
DatagramPacket sendPacket = new DatagramPacket(sendData,
sendData.length, InetAddress.getByName("X.X.X.X"), 7070);
clientSocket.send(sendPacket);
// receive Data ==> Format:"<IP of other Client>-<Port of other Client>"
DatagramPacket receivePacket = new DatagramPacket(new byte[1024], 1024);
clientSocket.receive(receivePacket);
// Convert Response to IP and Port
String response = new String(receivePacket.getData());
String[] splitResponse = response.split("-");
InetAddress ip = InetAddress.getByName(splitResponse[0].substring(1));
int port = Integer.parseInt(splitResponse[1]);
// output converted Data for check
System.out.println("IP: " + ip + " PORT: " + port);
// close socket and open new socket with SAME localport
int localPort = clientSocket.getLocalPort();
clientSocket.close();
clientSocket = new DatagramSocket(localPort);
// set Timeout for receiving Data
clientSocket.setSoTimeout(1000);
// send 5000 Messages for testing
for (int i = 0; i < 5000; i++) {
// send Message to other client
sendData = ("Datapacket(" + i + ")").getBytes();
sendPacket = new DatagramPacket(sendData, sendData.length, ip, port);
clientSocket.send(sendPacket);
// receive Message from other client
try {
receivePacket.setData(new byte[1024]);
clientSocket.receive(receivePacket);
System.out.println("REC: "
+ new String(receivePacket.getData()));
} catch (Exception e) {
System.out.println("SERVER TIMED OUT");
}
}
// close connection
clientSocket.close();
}
更新 代码基本上是可用的。我现在已经在两个不同的家庭网络中尝试过它，它可以运行。但是在我的3G或大学网络中无法工作。在3G中，我已经验证了NAT再次映射这两个端口（客户端端口和路由器分配的端口），即使在关闭和打开clientSocket之后也是如此。有人知道为什么它不起作用吗？