Android的 - 转换TCP客户端UDP客户

问题描述：

我有运行与发送和接收TCP连接的工作代码。这里是我的CreateCommThreadTask，WriteToServer和CloseSocketTask类：Android的 - 转换TCP客户端UDP客户

private class CreateCommThreadTask extends AsyncTask 
     <Void, Integer, Void> { 
    @Override 
    protected Void doInBackground(Void... params) { 
     try { 
      //---create a socket--- 
      serverAddress = 
        InetAddress.getByName("192.168.4.1"); 
      socket = new Socket(serverAddress, 8080); 
      commsThread = new CommsThread(socket); 
      commsThread.start(); 
     } catch (UnknownHostException e) { 
      Log.d("Sockets", e.getLocalizedMessage()); 
     } catch (IOException e) { 
      Log.d("Sockets", e.getLocalizedMessage()); 
     } 
     return null; 
    } 
} 

private class WriteToServerTask extends AsyncTask 
     <byte[], Void, Void> { 
    protected Void doInBackground(byte[]...data) { 
     commsThread.write(data[0]); 
     return null; 
    } 
} 

private class CloseSocketTask extends AsyncTask 
     <Void, Void, Void> { 
    @Override 
    protected Void doInBackground(Void... params) { 
     try { 
      socket.close(); 
     } catch (IOException e) { 
      Log.d("Sockets", e.getLocalizedMessage()); 
     } 
     return null; 
    } 
}

，并用这个类我读的输入数据：

public class CommsThread extends Thread { 
private final Socket socket; 
private final InputStream inputStream; 
private final OutputStream outputStream; 

public CommsThread(Socket sock) { 
    socket = sock; 
    InputStream tmpIn = null; 
    OutputStream tmpOut = null; 
    try { 
     //---creates the inputstream and outputstream objects 
     // for reading and writing through the sockets--- 
     tmpIn = socket.getInputStream(); 
     tmpOut = socket.getOutputStream(); 
    } catch (IOException e) { 
     Log.d("SocketChat", e.getLocalizedMessage()); 
    } 
    inputStream = tmpIn; 
    outputStream = tmpOut; 
} 

public void run() { 
    //---buffer store for the stream--- 
    byte[] buffer = new byte[1024]; 

    //---bytes returned from read()--- 
    int bytes; 

    //---keep listening to the InputStream until an 
    // exception occurs--- 
    while (true) { 
     try { 
      //---read from the inputStream--- 
      bytes = inputStream.read(buffer); 

      //---update the main activity UI--- 
      SocketsActivity.UIupdater.obtainMessage(
       0,bytes, -1, buffer).sendToTarget(); 
     } catch (IOException e) { 
      break; 
     } 
    } 
} 

//---call this from the main activity to 
// send data to the remote device--- 
public void write(byte[] bytes) { 
    try { 
     outputStream.write(bytes); 
    } catch (IOException e) { } 
} 

//---call this from the main activity to 
// shutdown the connection--- 
public void cancel() { 
    try { 
     socket.close(); 
    } catch (IOException e) { } 
} 

}

最后我用用Handler像这样我接收到的数据：

static Handler UIupdater = new Handler() { 
    @Override 
    public void handleMessage(Message msg) { 
     int numOfBytesReceived = msg.arg1; 
     byte[] buffer = (byte[]) msg.obj; 


     //---convert the entire byte array to string--- 
     //---extract only the actual string received--- 
     if(numOfBytesReceived>0) 
     { 
      strReceived = new String(buffer); 
      strReceived = strReceived.substring(0, numOfBytesReceived); 
     } 
     //---display the text received on the TextVie*--- 

    } 
};

这些代码在TCP连接的罚款。我的问题是需要进行哪些更改才能将它们转换为UDP客户端？我想在AsyncTask中实现UDP，与我写的TCP代码相同。

答

您应该使用DatagramSocket和DatagramPacket。这是一个很好的教程 - Writing a Datagram Client and Server。

答

要使用UDP，您应该使用DatagramSocket

要发送消息：

DatagramSocket serverSocket = new DatagramSocket(); 
InetAddress IPAddress = InetAddress.getByName(ipAddress); 
byte[] sendData = message.getBytes(); 
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, port); 
serverSocket.send(sendPacket);

要收到一条消息：

byte[] receiveData = new byte[15]; //max length 15. 
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length); 
DatagramSocket clientSocket = new DatagramSocket(port); 
clientSocket.receive(receivePacket); 
String receivedMessage = new String(receivePacket.getData()).trim();

我如何使用它完全像我写的代码TCP？（的AsyncTask） –

答

TCP & UDP之间的主要区别是，TCP是一个连接的套接字，你首先需要建立一个连接然后发送或接收数据包。与UDP不同，您可以直接将数据包发送到IP +目的地端口，而无需以前的连接，它是一个未连接的套接字。

随着UDP数据包的大小是有限的，建议不要超过512个字节，而不是用TCP还有的没有限制。

使用UDP不能保证数据包会在另一边接收，发送者不会有它是否收到任何确认，而不是在TCP有这样的验证。

如果你需要确保发送在另一侧被接收的字节数，你需要使用TCP和UDP不

而且还知道，其实有些手机公司不分配任何更多的连接公共IP给客户端，他们分配私有IP。在这种情况下，Android设备不能充当服务器，这意味着无法等待接收到的UDP数据包，并且由于其端口无法从WAN访问而无法侦听传入的TCP连接。

Android的 - 转换TCP客户端UDP客户

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