[英]Receive UDP packets fast
我有一个UDP侦听器线程,该线程被循环并在接收到数据包后调用方法。 它工作得很好,只是在第一个数据包之后很快到达多个数据包时,不会调用该方法。
一次发送两个数据包,第一个为2字节长,第二个为3字节长。 当第二个数据包到达时,大多会触发receive()方法。
这是UDP侦听器类:
public class UDPListener extends Thread{
private boolean running = true;
byte[] data = new byte[1500];
DatagramPacket packet = new DatagramPacket(data, data.length);
public void run() {
Log.v("MR", "Runs");
try {
while(running) {
Log.v("MR", "Listening... ");
socket.receive(packet);
Log.v("MR", "Received Data: " + packet.getData()[0] + "; Length: " + packet.getLength());
device.post(new Runnable() {
public void run() {
device.receive(packet.getData(), packet.getData().length);
}
});
}
} catch (Throwable e) {
e.printStackTrace();
Log.v("MR", "Failed receiving");
}
}
}
这是device.receive()方法:
public final void receive(byte[] inData, int length) {
data = inData;
dataLength = length;
Log.v("MR", "Receive(): Data: +" + data[0] + "; Length: " + String.valueOf(data.length));
}
这是Log结果的一部分:
10-18 17:24:34.393 Received Data: 79; Length: 3
10-18 17:24:34.393 Listening...
10-18 17:24:34.393 Receive(): Data: +79; Length: 1500
10-18 17:24:34.393 Receive(): Data: +79; Length: 1500
10-18 17:24:34.413 Received Data: 6; Length: 2
10-18 17:24:34.413 Listening...
10-18 17:24:34.413 Received Data: 79; Length: 3
10-18 17:24:34.413 Listening...
10-18 17:24:34.413 Receive(): Data: +79; Length: 1500
10-18 17:24:34.413 Receive(): Data: +79; Length: 1500
10-18 17:24:34.423 Received Data: 6; Length: 2
10-18 17:24:34.423 Listening...
可以看出,实际上有数据包进来,只是第二个(长度:3)数据包才经常调用receive()。
“设备”是带有receive()方法的自定义视图。 我也尝试使用处理程序和具有Runnable的runOnUiThread(),但结果相同。 我认为UI线程不能这么快或类似的更新。
另外,为什么在线程日志中具有实际长度而在resume()日志中具有1500字节的数据包呢? 应该是传递的相同数据包。
我看到这个问题有80多种观点。 解决方案是使用处理程序将消息发送到UI,并在新数据包出现之前重新初始化data []数组和DatagramPacket。
工作代码为:
public static class UDPListener extends Thread{
private boolean running = true;
Message msg;
byte[] data;
DatagramPacket packet;
public void run() {
try {
while(running) {
data = new byte[1500];
packet = new DatagramPacket(data, data.length);
//Blocks and waits for a packet
socket.receive(packet);
//Send packet message to UI
msg = UDPReceiveHandler.obtainMessage();
msg.obj = packet;
UDPReceiveHandler.sendMessage(msg);
}
} catch (Throwable e) {
e.printStackTrace();
}
}
}
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