[英]Receive UDP packets fast
我有一個UDP偵聽器線程,該線程被循環並在接收到數據包后調用方法。 它工作得很好,只是在第一個數據包之后很快到達多個數據包時,不會調用該方法。
一次發送兩個數據包,第一個為2字節長,第二個為3字節長。 當第二個數據包到達時,大多會觸發receive()方法。
這是UDP偵聽器類:
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");
}
}
}
這是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));
}
這是Log結果的一部分:
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,實際上有數據包進來,只是第二個(長度:3)數據包才經常調用receive()。
“設備”是帶有receive()方法的自定義視圖。 我也嘗試使用處理程序和具有Runnable的runOnUiThread(),但結果相同。 我認為UI線程不能這么快或類似的更新。
另外,為什么在線程日志中具有實際長度而在resume()日志中具有1500字節的數據包呢? 應該是傳遞的相同數據包。
我看到這個問題有80多種觀點。 解決方案是使用處理程序將消息發送到UI,並在新數據包出現之前重新初始化data []數組和DatagramPacket。
工作代碼為:
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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