您收到一个您没有发现的错误:NetworkOnMainThreadException。您应该在另一个 Thread 或 AsyncTask 中执行所有网络人员。
例如:
class MyThread extends Thread
{
@Override
public void run()
{
UDPSend();
}
void UDPSend()
{
String messageStr = "Hello Android!";
int server_port = 54372;
try
{
DatagramSocket s = new DatagramSocket();
InetAddress local = null;
local = InetAddress.getByName("192.168.1.57");
int msg_length = messageStr.length();
byte[] message = messageStr.getBytes();
DatagramPacket p = new DatagramPacket(message, msg_length, local, server_port);
s.send(p);
android.util.Log.w("UDP", "Works fine!");
}
catch (SocketException e)
{
e.printStackTrace();
}
catch (UnknownHostException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
catch (Exception e)
{
android.util.Log.w("UDP", "Catched here.");
e.printStackTrace();
}
}
}
要在主线程中执行线程:new MyThread().start();
更新:
Asynctask 中的 UDP 接收器:这是一个应用程序的真实示例。我删除了一些不相关的行。我向您展示 doInBackgroud,它接收 UDP 数据包。
@Override
protected Void doInBackground(Void... urls)
{
DatagramSocket socketUDP;
try
{
socketUDP = new DatagramSocket(5050);
socketUDP.setSoTimeout(5000);
// set it to true if you want to receive broadcast packets
socketUDP.setBroadcast(false);
}
catch (Exception e)
{
e.printStackTrace();
return null;
}
byte[] buff = new byte[512];
DatagramPacket packet = new DatagramPacket(buff, buff.length);
try
{
asyncTask_UDP_is_running=true;
// Keep running until application gets inactive
while (aplicationActive)
{
try
{
socketUDP.receive(packet);
android.util.Log.w("UDP", "got a packet");
}
catch (java.net.SocketTimeoutException ex)
{
// timeout
}
catch (Exception e)
{
e.printStackTrace();
return null;
}
}
}
finally
{
asyncTask_UDP_is_running=false;
}
return null;
}
}