Android-手机之间的UDP连接

Question

我正在学习网络课程，并被分配了一个可以在任何语言或环境中完成的项目。作为 Android 爱好者，我自然想在手机上实现这一点。我遇到问题的部分应该很简单，我开始认为我无法在手机之间使用 UDP 建立连接。我想做的是使用一部手机作为服务器，一部作为客户端。客户端向服务器发送消息，服务器将字符串更改为大写。 （这不是该项目，但这是看看它是否有效的一个很好的步骤。）有谁知道为什么服务器和客户端无法连接或者是否有可能？

这是服务器，下面是客户端、主启动屏幕和 main.xml

package com.csc.networking;
import java.net.*;

import android.util.Log;


public class UDPServer
{

   public void main() throws Exception
   {
       Log.d("s","1");
       DatagramSocket serverSocket = new DatagramSocket(6699);//create a datagram socket at the specified port number
       byte[] receiveData = new byte[1024];
       byte[] sendData = new byte[1024];
       Log.d("s","2");
       while(true)
       {
           Log.d("s","3");
           DatagramPacket receivePacket = new DatagramPacket(receiveData,receiveData.length);
           //To Do: construct a DatagramPacket object called receivePacket. Use the constructor of the class DatagramPacket
           //that takes two parameters: 1. the array of bytes (receiveData) and 2. the length of that array. 
           Log.d("s","3.5");
           //To Do: use the method receive on the DatagramSocket object to receive the packet sent from the client. 
           //the method receive takes one parameter (the DatagramPacket object constructed in the above step). 


           serverSocket.receive(receivePacket);
           Log.d("s","again");

           Log.d("s","3.75");
           String sentence = new String(receivePacket.getData());//extract the String from the array of bytes.
           Log.d("s",sentence);
           Log.d("s","4");
           InetAddress IPAddress = receivePacket.getAddress();//extract the IP address of the client

           int port = receivePacket.getPort();//extract the port number from the packet

           String capitalizedSentence = sentence.toUpperCase();//change the sentence received by the server
           sendData = capitalizedSentence.getBytes();//convert it to an array of bytes
           Log.d("s","5");
           DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, port);
           //To Do: construct a DatagramPacket object called sendPacket. Use the constructor of the class DatagramPacket
           //that takes 4 parameters: 1. the array of bytes to be sent. 2. the length of that array of bytes. 
           //3. the IP address of the client (use the object IPAddress) and 4. the port number of the process running in 
           //the client. 

           //To Do: send the packet to the client using the method send on the DatagramSocket object. The metho send
           //takes one parameter which is the packet constructed in the above step. 
           Log.d("s","5.5");
           serverSocket.send(sendPacket );
           Log.d("s","6");  
        }
    }

}





package com.csc.networking;

import java.io.*;
import java.net.*;

import android.util.Log;
import android.widget.*;



public class UDPClient {
     public void main(String string) throws Exception 
       {
         Log.d("help", "1");
         //EditText connectAddress = (EditText)findViewById(R.id.connectAddress);
         Log.d("help", "2");
         String hostIP = "10.60.5.79"; //connectAddress.getText().toString();
         Log.d("help", "3");
         String coded = string;
         Log.d("help", "4");
           DatagramSocket clientSocket = new DatagramSocket();//this line creates a datagram socket, this does not
           //create a TCP connection with the server, note how we do not have server and process info as parameters to 
           //the constructor
           Log.d("help", "5");

           InetAddress IPAddress = InetAddress.getByName(hostIP); //this line invokes DNS to lookup the IP address
           //of the hostname. If IP address is provided, it stores it in the object IPAddress.
           Log.d("help", "6");
           byte[] sendData = new byte[1024]; //array of bytes to be sent to server
           Log.d("help", "7");
           byte[] receiveData = new byte[1024]; //array of bytes that client will receive from server

           Log.d("help", "8");


           sendData = coded.getBytes(); //this converts sentence to an array of bytes and stores it in sendData. 
           Log.d("help", "9");
           DatagramPacket sendPacket = new DatagramPacket(sendData,sendData.length,IPAddress,6699);
           //To DO: construct a DatagramPacket object called sendPacket. The constructor of the DatagramPacket class
           //takes the following parameters: 1. the array of bytes to be sent. 2. the length of the array of bytes. 
           //3. the IPAddress of the destination (use the object IPAddress) and 4. the port number of the process running
           //at the destination. 
           Log.d("help", "10");
           clientSocket.send(sendPacket);
           //To DO: call the method send on the DatagramSocket object to send the datagram packet. The method send takes
           //the DatagramPacket object as a prameter and sends it through the socket. 
           Log.d("help", "11");
           DatagramPacket receivePacket = new DatagramPacket(receiveData,receiveData.length);
           //To Do: construct a new DatagramPacket object called recievePacket. This is the packet that the client will
           //receive from the destination. Use the constructor that takes two parameters: 1. an array of bytes (receiveData) and
           //2. the length of that array. 
           Log.d("help", "12");
           clientSocket.receive(receivePacket);
           //To Do: use the method receive on the DatagramSocket object to receive the datagram packet from the server. 
           //The method receive takes a parameter which is the DatagramPacket constructed in the above step. 

           Log.d("help", "13");
           String modifiedSentence = new String(receivePacket.getData());//this converts an array of bytes to a string.

           Log.d("help", "14");
           TextView decoded = (TextView)findViewById(R.id.decoded);
           Log.d("help", "15");
           decoded.setText(modifiedSentence);
           Log.d("help", "16");
           clientSocket.close();//this closes the connection. 
           Log.d("help", "17");
       }

    private EditText findViewById(int connectaddress) {
        // TODO Auto-generated method stub
        return null;
    }
}




 <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:baselineAligned="true" android:orientation="vertical"
        android:layout_width="wrap_content" android:layout_height="fill_parent">


        <TextView android:text="@string/Title" android:id="@+id/Title"
            android:layout_width="fill_parent" android:gravity="center"
            android:textSize="24px" android:layout_height="wrap_content" />


        <EditText android:id="@+id/editText1" android:layout_below="@+id/Title"
            android:layout_alignLeft="@+id/Title" android:layout_alignRight="@+id/Title"
             android:layout_width="fill_parent"
            android:layout_height="wrap_content" android:scrollbarAlwaysDrawVerticalTrack="true" android:scrollbars="vertical" android:singleLine="true" android:hint="@string/Hint"/>

        <RelativeLayout android:layout_width="wrap_content"
            android:layout_below="@+id/editText1" android:id="@+id/relativeLayout1"
            android:layout_height="wrap_content" android:layout_alignLeft="@+id/editText1"
            android:layout_alignRight="@+id/editText1">
            <Button android:layout_width="wrap_content"
                android:layout_below="@+id/startServer" android:layout_height="wrap_content"
                android:layout_alignLeft="@+id/startServer"
                android:layout_alignRight="@+id/startServer" android:id="@+id/Send"
                android:text="@string/Send" />
            <EditText android:layout_width="wrap_content" android:layout_below="@+id/Send" android:layout_height="wrap_content" android:layout_alignLeft="@+id/Send" android:layout_alignRight="@+id/Send" android:id="@+id/connectAddress" android:hint="Enter Ip Address Here"></EditText>
            <TextView android:text="Decoded" android:layout_width="wrap_content" android:layout_below="@+id/connectAddress" android:id="@+id/decoded" android:layout_height="wrap_content" android:layout_alignLeft="@+id/connectAddress" android:layout_alignRight="@+id/connectAddress"></TextView>
            <Button android:layout_width="fill_parent" android:id="@+id/startServer" android:text="@string/Start " android:layout_height="wrap_content" android:layout_alignParentRight="true"></Button>
        </RelativeLayout>





    </RelativeLayout>

package com.csc.networking;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class launchScreen extends Activity {


    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {


        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Button SendButton = (Button)findViewById(R.id.Send);
        SendButton.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {
                    try {
                        Log.d("click", "1");
                        EditText codedMessage = (EditText)findViewById(R.id.editText1);
                        UDPClient client = new UDPClient();
                        String msg = codedMessage.getText().toString();
                        Log.d("click", msg);
                        Log.d("click", "2");
                        client.main(msg);
                        Log.d("click", "3");
                    } catch (Exception e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
            }
        });
        Button ServerButton = (Button)findViewById(R.id.startServer);
        ServerButton.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {
                try {
                    UDPServer server = new UDPServer();
                    server.main();
                }
                catch (Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                }
            });
    }

}

Answer 1

http://systembash.com/content/a- simple-java-udp-server-and-udp-client/

这应该就是您正在寻找的！
此致

Answer 2

首先，您正在尝试在 UI 线程上执行网络操作。在较新的Android中它会导致异常，并且用户体验非常糟糕。当服务器或客户端在方法中等待时：

socket.receive() 

更好的主意是将这些东西放入线程或 AsyncTasks 中。这可能对网络 android 中的网络

根据您的问题有所帮助，我建议多次发送此数据包。 UDP 不保证数据包传送，并且仅发送一个数据包是相当危险的。

将您的 socket.send() 方法放入循环中并发送 10 次相同的数据包。

您也可以尝试将其发送到您的计算机IP地址，并使用诸如
Wireshark 如果收到。

最后但并非最不重要的一点是，在您的情况下，更好的选择是 TCP 客户端和服务器，这样可以保证数据包的传送。 UDP 最适合流媒体等，在这些情况下重传根本没有用处。

Answer 3

如果您使用 3G 连接，入站防火墙可能会阻止您的（传入）连接。请参阅此

我的建议是从无线本地网络开始，所以IP 将是静态/众所周知的，然后转移到互联网连接。