[英]Unable to manage multiple clients (android devices) for a single java server
我需要服务器来跟踪每个客户端的连接。 建议我使用线程。 所以我想要实现的是为每个客户端创建一个线程,该线程应运行到客户端连接存在为止。 但是发生的是,对于任何客户端发送的每条消息,都在doInBackground()函数中创建了一个新的客户端连接。 因此,我没有为一个客户端使用一个线程,而是为发送到服务器的任何客户端消息使用了一个线程。 您能否提出一种方法,使我的服务器能够区分来自不同客户端的不同消息?
Java服务器代码:
package com.nss.academyassistserver;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
public class AcademyAssistServer {
public static ServerSocket serverSocket;
public static Socket clientSocket;
static final int PORT = 4444;
public static void main(String[] args) {
// TODO Auto-generated method stub
try {
serverSocket = new ServerSocket(PORT); // Server socket
} catch (IOException e) {
System.out.println("Could not listen on port: "+PORT+" \n");
}
System.out.println("Server started. Listening to the port "+PORT);
while (true) {
try {
clientSocket = serverSocket.accept();
System.out.println("New connection accepted."); // accept the client connection
} catch (IOException ex) {
System.out.println("Problem in message reading");
}
//new thread for a client
new EchoThread(clientSocket).start();
}
}
}
class EchoThread extends Thread {
InputStreamReader inputStreamReader;
BufferedReader bufferedReader;
String fromClient;
Socket clientSocket;
public EchoThread(Socket clientSocket) {
this.clientSocket = clientSocket;
}
public void run() {
try {
inputStreamReader = new InputStreamReader(clientSocket.getInputStream());
bufferedReader = new BufferedReader(inputStreamReader); // get the client message
} catch (IOException e) {
return;
}
while (!Thread.currentThread().isInterrupted()) {
System.out.println("I am thread " + Thread.currentThread().getId());
try {
fromClient = bufferedReader.readLine();
if ((fromClient == null) || fromClient.equalsIgnoreCase("exit")) {
System.out.println("You're welcome, bye!");
return;
} else {
System.out.println(fromClient);
Thread.currentThread().interrupt();
}
} catch (IOException e) {
e.printStackTrace();
return;
}
}
try {
clientSocket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
客户活动代码:
package com.nss.academyassist;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Locale;
//import statements for client
import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.Toast;
//import statements for client
import android.os.AsyncTask;
public class MainActivity extends Activity implements OnClickListener {
EditText question;
//Client sockets
private Socket client;
private PrintWriter printwriter;
private String toTag;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
question = (EditText)findViewById(R.id.editText1);
Button query = (Button)findViewById(R.id.button2);
query.setOnClickListener(this);
}
private class SendMessage extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... params) {
try {
client = new Socket("Server IP Address", 4444);
printwriter = new PrintWriter(client.getOutputStream(), true);
printwriter.write(toTag); // write the message to output stream
printwriter.flush();
printwriter.close();
client.close(); // closing the connection
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
public void onClick(View v)
{
switch(v.getId())
{
case R.id.button2:
toTag = question.getText().toString();
// Output the result
Toast.makeText(getApplicationContext(), toTag,
Toast.LENGTH_LONG).show();
//Invoke the execute method of AsynTask, which will run the doInBackground method of SendMessage Class
SendMessage sendMessageTask = new SendMessage();
sendMessageTask.execute();
break;
}
}
}
您可以使用IP告诉客户端。 采用
clientSocket.getInetAddress().getHostAddress()
您还可以在android代码中保持客户端未关闭。 例如,您可以在onCreate
打开Socket
并在onDestroy
中将其close
。
问题的原因在于您的客户端代码。 使用new Socket(..)
客户端每次向服务器发送标签时都会创建一个新的连接。 因此,您可以创建一个可以重用的连接:
public class MainActivity extends Activity implements OnClickListener {
/* .. your other variables .. */
private Socket client;
private PrintWriter printwriter;
@Override
protected void onCreate(Bundle savedInstanceState) {
/* .. no change here .. */
}
public void onStart()
{
if(this.client != null)
{
try {
client = new Socket("Server IP Address", 4444);
printwriter = new PrintWriter(client.getOutputStream(), true);
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public void onClose()
{
this.printwriter.close();
this.printwriter = null;
this.client.close();
this.client = null;
}
private class SendMessage extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... params) {
try {
printwriter.write(toTag); // write the message to output stream
printwriter.write("\n"); // delimiter
printwriter.flush();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
public void onClick(View v)
{
switch(v.getId())
{
case R.id.button2:
toTag = question.getText().toString();
// Output the result
Toast.makeText(getApplicationContext(), toTag,
Toast.LENGTH_LONG).show();
//Invoke the execute method of AsynTask, which will run the doInBackground method of SendMessage Class
SendMessage sendMessageTask = new SendMessage();
sendMessageTask.execute();
break;
}
}
}
除此之外,您还应该在标签/消息中附加一些定界符,以便服务器能够将内容与其他消息区分开。
由于您正在使用BufferedReader.readLine()分隔行
由换行符('\\ n'),回车符('\\ r')或回车符中的任意一个后跟换行符
为此,我在上面的示例中添加了一行,该行在该标记之后附加一个换行符。
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