udp_j2me.txt

j2me udp code

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   您现在的位置： J2ME开发网 >> 文章 >> J2ME开发指南 >> 联网开发 >> [专题]J2ME联网开发专题 >> 正文  2004年12月14日 星期二   
  J2ME中使用socket开发联网程序     热 荐    
 
J2ME中使用socket开发联网程序  
［ 作者：mingjava    转贴自：本站原创    点击数：443    更新时间：2004-12-1    文章录入：mingjava ］ 
 
在J2ME中基于UDP协议编程一文中介绍了如何使用Datagram和DatagramConnection来开发应用程序，本文将主要讲述在MIDP2.0中使用ServerSocketConnection和SocketConnection来开发联网应用程序。TCP协议是可以保证传输的质量的，这也是他和UDP的一大区别。由于以上谈到的四个类都属于GCF，他们在程序编写方面也非常相似，通常我们在Server端的某个端口监听，当客户端连接服务器的时候，则可以得到一个SocketConnection的实例。通过两端的SocketConnection则可以实现C/S结构的通信了。

    首先看一下，ServerSocketConnection类，它的一个非常重要的方法就是acceptAndOpen()方法，这个方法返回一个SocketConnection实例，从而使得客户端和服务器端可以通过socket通信了。典型的代码如下：

// Create the server listening socket for port 1234 
   ServerSocketConnection scn = (ServerSocketConnection)
                            Connector.open("socket://:1234");

   // Wait for a connection.
   SocketConnection sc = (SocketConnection) scn.acceptAndOpen();

   // Set application specific hints on the socket.
   sc.setSocketOption(DELAY, 0);
   sc.setSocketOption(LINGER, 0);
   sc.setSocketOption(KEEPALIVE, 0);
   sc.setSocketOption(RCVBUF, 128);
   sc.setSocketOption(SNDBUF, 128);

   // Get the input stream of the connection.
   DataInputStream is = sc.openDataInputStream();

   // Get the output stream of the connection.
   DataOutputStream os = sc.openDataOutputStream();

   // Read the input data.
   String result = is.readUTF();

   // Echo the data back to the sender.
   os.writeUTF(result);

   // Close everything.
   is.close();
   os.close();
   sc.close();
   scn.close();
   ..
    

    SocketConnection的使用也是非常简单，通过Connector的open方法我们可以得到一个SocketConnection的实例。
   SocketConnection sc = (SocketConnection)
                         Connector.open("socket://host.com:79");
   sc.setSocketOption(SocketConnection.LINGER, 5);

   InputStream is  = sc.openInputStream();
   OutputStream os = sc.openOutputStream();

   os.write("\r\n".getBytes());
   int ch = 0;
   while(ch != -1) {
       ch = is.read();
   }

   is.close();
   os.close();
   sc.close();
 其实我们在用socket编写程序的时候无非遵循这样的一种规则：服务器端建立监听端口等待连接，客户端通过open()方法与服务器端建立连接，两端通过建立的socket传输数据，关闭连接。

    下图是我在运行WTK中NetworkDemo的时候的截图!代码也一并贴出来。


 

 

 

 

 

 

 

 

package socket;

import javax.microedition.midlet.*;
import javax.microedition.io.*;
import javax.microedition.lcdui.*;
import java.io.*;

public class SocketMIDlet extends MIDlet implements CommandListener {

 private static final String SERVER = "Server";

 private static final String CLIENT = "Client";

 private static final String[] names = { SERVER, CLIENT };

 private static Display display;

 private Form f;

 private ChoiceGroup cg;

 private boolean isPaused;

 private Server server;

 private Client client;

 private Command exitCommand = new Command("Exit", Command.EXIT, 1);

 private Command startCommand = new Command("Start", Command.ITEM, 1);

 public SocketMIDlet() {

  display = Display.getDisplay(this);
  f = new Form("Socket Demo");
  cg = new ChoiceGroup("Please select peer", Choice.EXCLUSIVE, names,
    null);
  f.append(cg);

  f.addCommand(exitCommand);
  f.addCommand(startCommand);
  f.setCommandListener(this);

  display.setCurrent(f);
 }

 public boolean isPaused() {
  return isPaused;
 }

 public void startApp() {
  isPaused = false;
 }

 public void pauseApp() {
  isPaused = true;
 }

 public void destroyApp(boolean unconditional) {
  if (server != null) {
   server.stop();
  }
  if (client != null) {
   client.stop();
  }
 }

 public void commandAction(Command c, Displayable s) {
  if (c == exitCommand) {
   destroyApp(true);
   notifyDestroyed();
  } else if (c == startCommand) {
   String name = cg.getString(cg.getSelectedIndex());
   if (name.equals(SERVER)) {
    server = new Server(this);
    server.start();
   } else {
    client = new Client(this);
    client.start();
   }
  }
 }

}

package socket;

import javax.microedition.midlet.*;
import javax.microedition.io.*;
import javax.microedition.lcdui.*;
import java.io.*;

public class Server implements Runnable, CommandListener {
 private SocketMIDlet parent;

 private Display display;

 private Form f;

 private StringItem si;

 private TextField tf;

 private boolean stop;

 private Command sendCommand = new Command("Send", Command.ITEM, 1);

 private Command exitCommand = new Command("Exit", Command.EXIT, 1);

 InputStream is;

 OutputStream os;

 SocketConnection sc;

 ServerSocketConnection scn;

 Sender sender;

 public Server(SocketMIDlet m) {
  parent = m;
  display = Display.getDisplay(parent);
  f = new Form("Socket Server");
  si = new StringItem("Status:", " ");
  tf = new TextField("Send:", "", 30, TextField.ANY);
  f.append(si);
  f.append(tf);
  f.addCommand(exitCommand);
  f.setCommandListener(this);
  display.setCurrent(f);
 }

 public void start() {
  Thread t = new Thread(this);
  t.start();
 }

 public void run() {
  try {
   si.setText("Waiting for connection");
   scn = (ServerSocketConnection) Connector.open("socket://:5009");

   // Wait for a connection.
   sc = (SocketConnection) scn.acceptAndOpen();
   si.setText("Connection accepted");
   is = sc.openInputStream();
   os = sc.openOutputStream();
   sender = new Sender(os);

   // Allow sending of messages only after Sender is created
   f.addCommand(sendCommand);

   while (true) {
    StringBuffer sb = new StringBuffer();
    int c = 0;

    while (((c = is.read()) != '\n') && (c != -1)) {
     sb.append((char) c);
    }

    if (c == -1) {
     break;
    }
    si.setText("Message received - " + sb.toString());
   }
   stop();
   si.setText("Connection is closed");
   f.removeCommand(sendCommand);
  } catch (IOException ioe) {
   if (ioe.getMessage().equals("ServerSocket Open")) {
    Alert a = new Alert("Server", "Port 5000 is already taken.",
      null, AlertType.ERROR);
    a.setTimeout(Alert.FOREVER);
    a.setCommandListener(this);
    display.setCurrent(a);
   } else {
    if (!stop) {
     ioe.printStackTrace();
    }
   }
  } catch (Exception e) {
   e.printStackTrace();
  }
 }

 public void commandAction(Command c, Displayable s) {
  if (c == sendCommand && !parent.isPaused()) {
   sender.send(tf.getString());
  }

  if ((c == Alert.DISMISS_COMMAND) || (c == exitCommand)) {
   parent.notifyDestroyed();
   parent.destroyApp(true);
  }
 }

 /**
  * Close all open streams
  */
 public void stop() {
  try {
   stop = true;

   if (is != null) {
    is.close();
   }

   if (os != null) {
    os.close();
   }

   if (sc != null) {
    sc.close();
   }

   if (scn != null) {
    scn.close();
   }
  } catch (IOException ioe) {
  }
 }
}

package socket;

import javax.microedition.midlet.*;
import javax.microedition.io.*;
import javax.microedition.lcdui.*;
import java.io.*;

public class Client implements Runnable, CommandListener {
 private SocketMIDlet parent;

 private Display display;

 private Form f;

 private StringItem si;

 private TextField tf;

 private boolean stop;

 private Command sendCommand = new Command("Send", Command.ITEM, 1);

 private Command exitCommand = new Command("Exit", Command.EXIT, 1);

 InputStream is;

 OutputStream os;

 SocketConnection sc;

 Sender sender;

 public Client(SocketMIDlet m) {
  parent = m;
  display = Display.getDisplay(parent);
  f = new Form("Socket Client");
  si = new StringItem("Status:", " ");
  tf = new TextField("Send:", "", 30, TextField.ANY);
  f.append(si);
  f.append(tf);
  f.addCommand(exitCommand);
  f.addCommand(sendCommand);
  f.setCommandListener(this);
  display.setCurrent(f);
 }

 /**
  * Start the client thread
  */
 public void start() {
  Thread t = new Thread(this);
  t.start();
 }

 public void run() {
  try {
   sc = (SocketConnection) Connector.open("socket://localhost:5009");
   si.setText("Connected to server");
   is = sc.openInputStream();
   os = sc.openOutputStream();

   // Start the thread for sending messages - see Sender's main
   // comment for explanation
   sender = new Sender(os);

   // Loop forever, receiving data
   while (true) {
    StringBuffer sb = new StringBuffer();
    int c = 0;

    while (((c = is.read()) != '\n') && (c != -1)) {
     sb.append((char) c);
    }

    if (c == -1) {
     break;
    }

    // Display message to user
    si.setText("Message received - " + sb.toString());
   }
   stop();
   si.setText("Connection closed");
   f.removeCommand(sendCommand);
  } catch (ConnectionNotFoundException cnfe) {
   Alert a = new Alert("Client", "Please run Server MIDlet first",
     null, AlertType.ERROR);
   a.setTimeout(Alert.FOREVER);
   a.setCommandListener(this);
   display.setCurrent(a);
  } catch (IOException ioe) {
   if (!stop) {
    ioe.printStackTrace();
   }
  } catch (Exception e) {
   e.printStackTrace();
  }
 }

 public void commandAction(Command c, Displayable s) {
  if (c == sendCommand && !parent.isPaused()) {
   sender.send(tf.getString());
  }

  if ((c == Alert.DISMISS_COMMAND) || (c == exitCommand)) {
   parent.notifyDestroyed();
   parent.destroyApp(true);
  }
 }

 /**
  * Close all open streams
  */
 public void stop() {
  try {
   stop = true;

   if (sender != null) {
    sender.stop();
   }

   if (is != null) {
    is.close();
   }

   if (os != null) {
    os.close();
   }

   if (sc != null) {
    sc.close();
   }
  } catch (IOException ioe) {
  }
 }
}

package socket;

import javax.microedition.midlet.*;
import javax.microedition.io.*;
import javax.microedition.lcdui.*;
import java.io.*;

public class Sender extends Thread {

 private OutputStream os;

 private String message;

 public Sender(OutputStream os) {
  this.os = os;
  start();
 }

 public synchronized void send(String msg) {
  message = msg;
  notify();
 }

 public synchronized void run() {

  while (true) {

   // If no client to deal, wait until one connects
   if (message == null) {
    try {
     wait();
    } catch (InterruptedException e) {
    }
   }

   if (message == null) {
    break;
   }

   try {
    os.write(message.getBytes());
    os.write("\r\n".getBytes());
   } catch (IOException ioe) {
    ioe.printStackTrace();
   }

   // Completed client handling, return handler to pool and
   // mark for wait
   message = null;
  }
 }

 public synchronized void stop() {
  message = null;
  notify();
 }
}