Java 用applet实现客户机与服务器的通信
我对客户机-服务器编程比较陌生，我试图在applet gui上实现客户机和服务器之间的简单通信，它现在可以工作了，但是当我运行客户机时，我遇到了一个异常 修改代码： 客户：Java 用applet实现客户机与服务器的通信,java,sockets,applet,socketexception,Java,Sockets,Applet,Socketexception,我对客户机-服务器编程比较陌生，我试图在applet gui上实现客户机和服务器之间的简单通信，它现在可以工作了，但是当我运行客户机时，我遇到了一个异常 修改代码： 客户： import java.awt.*; import java.net.*; import java.io.*; import javax.swing.*; public class Client extends JApplet{ /** * */ private static f
import java.awt.*;
import java.net.*;
import java.io.*;
import javax.swing.*;
public class Client extends JApplet{
/**
*
*/
private static final long serialVersionUID = 1L;
private JTextArea displayArea;
private Socket socket = null;
private DataInputStream input;
private DataOutputStream output;
public void init()
{
Container container = getContentPane();
// set up JTextArea to display
displayArea = new JTextArea();
displayArea.setEditable(false);
container.add(new JScrollPane(displayArea), BorderLayout.SOUTH );
try
{
// make connection
socket = new Socket(getCodeBase().getHost(), 5423);
// get streams
input = new DataInputStream( socket.getInputStream() );
output = new DataOutputStream( socket.getOutputStream() );
while(true)
{
output.writeUTF("hello from client"); //send message to server
output.flush();
processMessage(input.readUTF()); //process data from server
}
}
// catch problems setting up connection and streams
catch ( IOException ioException ) {
ioException.printStackTrace();
}
try
{
input.close();
output.close();
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
// process message received by client
private void processMessage(String message)
{
if (message.equals("hello") )
{
displayMessage("Connected to server");
}
}
private void displayMessage(final String messageToDisplay)
{
SwingUtilities.invokeLater(
new Runnable() {
public void run()
{
displayArea.append(messageToDisplay);
displayArea.setCaretPosition(displayArea.getText().length());
}
}
);
}
}
import java.awt.*;
import java.net.*;
import java.io.*;
import javax.swing.*;
public class Client extends JApplet{
/**
*
*/
private static final long serialVersionUID = 1L;
private JTextArea displayArea;
private Socket socket = null;
private DataInputStream input;
private DataOutputStream output;
@Override
public void init()
{
Container container = getContentPane();
// set up JTextArea to display
displayArea = new JTextArea();
displayArea.setEditable(false);
container.add(new JScrollPane(displayArea), BorderLayout.SOUTH );
try
{
// make connection
socket = new Socket(getCodeBase().getHost(), 8020);
// get streams
input = new DataInputStream( socket.getInputStream() );
output = new DataOutputStream( socket.getOutputStream() );
output.writeUTF("hello from client"); //send message to server
processMessage(input.readUTF()); //process data from server
}
// catch problems setting up connection and streams
catch (IOException e)
{
e.printStackTrace();
}
}
// process message received by client
private void processMessage(String message) throws IOException
{
if (message.equals("hello") )
{
displayMessage("Connected to server");
}
}
private void displayMessage(final String messageToDisplay)
{
SwingUtilities.invokeLater(
new Runnable() {
public void run()
{
displayArea.append(messageToDisplay);
displayArea.setCaretPosition(displayArea.getText().length());
}
}
);
}
}
import java.awt.*;
import java.net.*;
import java.io.*;
import javax.swing.*;
public class Server extends JFrame{
/**
*
*/
private static final long serialVersionUID = 1L;
private ServerSocket serverSocket;
private JTextArea outputArea;
private Socket socket = null;
private DataInputStream input;
private DataOutputStream output;
public Server()
{
super("Server");
try
{
serverSocket = new ServerSocket(5423, 1);
}
catch(IOException ioException)
{
ioException.printStackTrace();
System.exit(1);
}
outputArea = new JTextArea();
getContentPane().add(outputArea, BorderLayout.CENTER);
outputArea.setText("Server awaiting connections\n");
setSize(300, 300);
setVisible(true);
}
private void doThis() throws IOException
{
try
{
while(true)
{
socket = serverSocket.accept();
input = new DataInputStream(socket.getInputStream());
output = new DataOutputStream(socket.getOutputStream());
output.writeUTF("hello");
outputArea.append(input.readUTF()); //receive data from client
output.flush();
}
}
catch(IOException e)
{
e.printStackTrace();
}
finally
{
output.close();
input.close();
socket.close(); //close connection to client
}
}
public static void main(String[] args) throws IOException
{
Server server = new Server();
server.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
server.doThis();
}
}
import java.awt.*;
import java.net.*;
import java.io.*;
import javax.swing.*;
public class Server extends JFrame{
/**
*
*/
private static final long serialVersionUID = 1L;
private JTextArea outputArea;
private DataInputStream input;
private DataOutputStream output;
public Server()
{
super("Server");
outputArea = new JTextArea();
getContentPane().add(outputArea, BorderLayout.CENTER);
SwingUtilities.invokeLater(
new Runnable() {
public void run()
{
outputArea.setText("Server awaiting connections\n");
}
}
);
setSize(300, 300);
setVisible(true);
}
private void doThis() throws IOException
{
ServerSocket serverSocket = null;
Socket socket = null;
try
{
serverSocket = new ServerSocket(8020, 1);
}
catch(IOException ioException)
{
ioException.printStackTrace();
System.exit(1);
}
try
{
while(true)
{
socket = serverSocket.accept();
input = new DataInputStream(socket.getInputStream());
output = new DataOutputStream(socket.getOutputStream());
output.writeUTF("hello"); //send a string to client
outputArea.append(input.readUTF()); //receive data from client and append the string to the text area
}
}
catch(IOException e)
{
e.printStackTrace();
}
finally
{
socket.close();
}
}
public static void main(String[] args)
{
new Thread(new Runnable()
{
@Override
public void run()
{
Server server = new Server();
server.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
try
{
server.doThis();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}).start();
}
}
现在您的服务器出现故障。
ServerSocket应该创建一次（就像在代码中一样），
然后ServerSocket listener应该等待接受新连接-每个客户端一个，只有当新客户端尝试连接时才会发生，
接受新客户端连接（）时，新线程应处理每个客户端，在该线程中，您应打开IO流一次，然后创建一个读取/写入/处理数据的循环，同样，在数据处理循环完成后，IO流只应关闭一次。尝试接受发布的建议，这次没有例外 客户：
import java.awt.*;
import java.net.*;
import java.io.*;
import javax.swing.*;
public class Client extends JApplet{
/**
*
*/
private static final long serialVersionUID = 1L;
private JTextArea displayArea;
private Socket socket = null;
private DataInputStream input;
private DataOutputStream output;
public void init()
{
Container container = getContentPane();
// set up JTextArea to display
displayArea = new JTextArea();
displayArea.setEditable(false);
container.add(new JScrollPane(displayArea), BorderLayout.SOUTH );
try
{
// make connection
socket = new Socket(getCodeBase().getHost(), 5423);
// get streams
input = new DataInputStream( socket.getInputStream() );
output = new DataOutputStream( socket.getOutputStream() );
while(true)
{
output.writeUTF("hello from client"); //send message to server
output.flush();
processMessage(input.readUTF()); //process data from server
}
}
// catch problems setting up connection and streams
catch ( IOException ioException ) {
ioException.printStackTrace();
}
try
{
input.close();
output.close();
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
// process message received by client
private void processMessage(String message)
{
if (message.equals("hello") )
{
displayMessage("Connected to server");
}
}
private void displayMessage(final String messageToDisplay)
{
SwingUtilities.invokeLater(
new Runnable() {
public void run()
{
displayArea.append(messageToDisplay);
displayArea.setCaretPosition(displayArea.getText().length());
}
}
);
}
}
import java.awt.*;
import java.net.*;
import java.io.*;
import javax.swing.*;
public class Client extends JApplet{
/**
*
*/
private static final long serialVersionUID = 1L;
private JTextArea displayArea;
private Socket socket = null;
private DataInputStream input;
private DataOutputStream output;
@Override
public void init()
{
Container container = getContentPane();
// set up JTextArea to display
displayArea = new JTextArea();
displayArea.setEditable(false);
container.add(new JScrollPane(displayArea), BorderLayout.SOUTH );
try
{
// make connection
socket = new Socket(getCodeBase().getHost(), 8020);
// get streams
input = new DataInputStream( socket.getInputStream() );
output = new DataOutputStream( socket.getOutputStream() );
output.writeUTF("hello from client"); //send message to server
processMessage(input.readUTF()); //process data from server
}
// catch problems setting up connection and streams
catch (IOException e)
{
e.printStackTrace();
}
}
// process message received by client
private void processMessage(String message) throws IOException
{
if (message.equals("hello") )
{
displayMessage("Connected to server");
}
}
private void displayMessage(final String messageToDisplay)
{
SwingUtilities.invokeLater(
new Runnable() {
public void run()
{
displayArea.append(messageToDisplay);
displayArea.setCaretPosition(displayArea.getText().length());
}
}
);
}
}
import java.awt.*;
import java.net.*;
import java.io.*;
import javax.swing.*;
public class Server extends JFrame{
/**
*
*/
private static final long serialVersionUID = 1L;
private ServerSocket serverSocket;
private JTextArea outputArea;
private Socket socket = null;
private DataInputStream input;
private DataOutputStream output;
public Server()
{
super("Server");
try
{
serverSocket = new ServerSocket(5423, 1);
}
catch(IOException ioException)
{
ioException.printStackTrace();
System.exit(1);
}
outputArea = new JTextArea();
getContentPane().add(outputArea, BorderLayout.CENTER);
outputArea.setText("Server awaiting connections\n");
setSize(300, 300);
setVisible(true);
}
private void doThis() throws IOException
{
try
{
while(true)
{
socket = serverSocket.accept();
input = new DataInputStream(socket.getInputStream());
output = new DataOutputStream(socket.getOutputStream());
output.writeUTF("hello");
outputArea.append(input.readUTF()); //receive data from client
output.flush();
}
}
catch(IOException e)
{
e.printStackTrace();
}
finally
{
output.close();
input.close();
socket.close(); //close connection to client
}
}
public static void main(String[] args) throws IOException
{
Server server = new Server();
server.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
server.doThis();
}
}
import java.awt.*;
import java.net.*;
import java.io.*;
import javax.swing.*;
public class Server extends JFrame{
/**
*
*/
private static final long serialVersionUID = 1L;
private JTextArea outputArea;
private DataInputStream input;
private DataOutputStream output;
public Server()
{
super("Server");
outputArea = new JTextArea();
getContentPane().add(outputArea, BorderLayout.CENTER);
SwingUtilities.invokeLater(
new Runnable() {
public void run()
{
outputArea.setText("Server awaiting connections\n");
}
}
);
setSize(300, 300);
setVisible(true);
}
private void doThis() throws IOException
{
ServerSocket serverSocket = null;
Socket socket = null;
try
{
serverSocket = new ServerSocket(8020, 1);
}
catch(IOException ioException)
{
ioException.printStackTrace();
System.exit(1);
}
try
{
while(true)
{
socket = serverSocket.accept();
input = new DataInputStream(socket.getInputStream());
output = new DataOutputStream(socket.getOutputStream());
output.writeUTF("hello"); //send a string to client
outputArea.append(input.readUTF()); //receive data from client and append the string to the text area
}
}
catch(IOException e)
{
e.printStackTrace();
}
finally
{
socket.close();
}
}
public static void main(String[] args)
{
new Thread(new Runnable()
{
@Override
public void run()
{
Server server = new Server();
server.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
try
{
server.doThis();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}).start();
}
}
例外情况是什么？嗨，我已经编辑了主要帖子，包括第41行附近的代码例外情况。这里发生了什么？再次查看抛出异常的行上方的第41-5行。你看到了什么？为什么要关闭循环中的IO流？在处理完所有数据后，应该只执行一次。我注意到，我不应该关闭客户端上的流，因为服务器正在请求返回字符串，我已经更改了它，以便在服务器上关闭流。我还删除了“while true”循环，因为它在这里没有任何用途，所以现在我没有得到任何异常。过一段时间，我会试着给自己的问题贴一个完整的答案，如果你认为我仍然在做一些奇怪的事情，如果你能编辑我的答案，我将不胜感激。