所以,正如标题所暗示的那样,我的Java项目遇到了一些问题。我想做的是:
我已经使用UDP广播完成了这个任务,但有时会失败。这些计算机通过WiFi连接,基本上是通过路由器连接。在许多情况下,任何一个运行X的计算机都可以通过我的UDP发现方法看到Y计算机,但有时不行,除非我手动指定IP,有时甚至连手动指定IP也不行。
以下是用于发现特定端口上监听服务器的代码:
- 我有两台运行应用程序X的计算机
- 还有另外三台运行应用程序Y的计算机
我已经使用UDP广播完成了这个任务,但有时会失败。这些计算机通过WiFi连接,基本上是通过路由器连接。在许多情况下,任何一个运行X的计算机都可以通过我的UDP发现方法看到Y计算机,但有时不行,除非我手动指定IP,有时甚至连手动指定IP也不行。
以下是用于发现特定端口上监听服务器的代码:
public static ArrayList<InetAddress> searchComputer() {
ArrayList<InetAddress> targets = new ArrayList<InetAddress>();
try {
c = new DatagramSocket();
c.setBroadcast(true);
byte[] sendData = "DISCOVER_PC_SERVER_REQUEST".getBytes();
try {
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, InetAddress.getByName("255.255.255.255"), 2005);
c.send(sendPacket);
} catch (Exception e) {}
Enumeration interfaces = NetworkInterface.getNetworkInterfaces();
while (interfaces.hasMoreElements()) {
NetworkInterface networkInterface = (NetworkInterface) interfaces.nextElement();
if (networkInterface.isLoopback() || !networkInterface.isUp()) {
continue;
}
for (InterfaceAddress interfaceAddress : networkInterface.getInterfaceAddresses()) {
InetAddress broadcast = interfaceAddress.getBroadcast();
if (broadcast == null) {
continue;
}
try {
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, broadcast, 8888);
c.send(sendPacket);
} catch (Exception e) { }
}
}
byte[] recvBuf = new byte[15000];
DatagramPacket receivePacket = new DatagramPacket(recvBuf, recvBuf.length);
if (useInstant) {
c.setSoTimeout(500);
}
else {
c.setSoTimeout(4000); //EXECUTE THE WHILE FOR 4 SECONDS, THEN RETURN WHATEVER THE RESULTS ARE.
}
while (true) {
c.receive(receivePacket);
String message = new String(receivePacket.getData()).trim();
if (message.equals("DISCOVER_PC_SERVER_RESPONSE")) {
// return receivePacket.getAddress();
targets.add(receivePacket.getAddress());
}
}
// c.close();
} catch (IOException ex){}
return targets;
}
这是我的“服务器”:
private void start_Discovery() throws Exception {
//Keep a socket open to listen to all the UDP trafic that is destined for this port
socket = new DatagramSocket(2005, InetAddress.getByName("0.0.0.0"));
socket.setBroadcast(true);
while (true) {
// System.out.println(getClass().getName() + ">>>Ready to receive broadcast packets!");
//Receive a packet
byte[] recvBuf = new byte[15000];
DatagramPacket packet = new DatagramPacket(recvBuf, recvBuf.length);
socket.receive(packet);
//Packet received
// System.out.println(getClass().getName() + ">>>Discovery packet received from: " + packet.getAddress().getHostAddress());
// System.out.println(getClass().getName() + ">>>Packet received; data: " + new String(packet.getData()));
//See if the packet holds the right command (message)
String message = new String(packet.getData()).trim();
if (message.equals("DISCOVER_ANDROID_SERVER_REQUEST")) {
byte[] sendData = "DISCOVER_ANDROID_SERVER_RESPONSE".getBytes();
//Send a response
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, packet.getAddress(), packet.getPort());
socket.send(sendPacket);
// System.out.println(getClass().getName() + ">>>Sent packet to: " + sendPacket.getAddress().getHostAddress());
}
}
}
为什么有时候即使他们连接到同一个路由器,但却看不到彼此呢?
EXTRA: 如果X台电脑通过局域网连接,而Y台电脑通过WiFi连接,会有特殊情况吗?