Socket网络编程报异常
Client类
- Java code
package ex30;import java.io.*;import java.net.*;import java.awt.*;import java.awt.event.*;import javax.swing.*;public class Client extends JFrame{ // Text field for receiving radius private JTextField jtf = new JTextField(); // Text area to display contents private JTextArea jta = new JTextArea(); // IO streams private DataOutputStream toServer; private DataInputStream fromServer; public static void main(String[] args) { // TODO 自动生成方法存根 new Client(); } public Client(){ // Panel p to hold the label and text field JPanel p = new JPanel(); p.setLayout(new BorderLayout()); p.add(new JLabel("Enter radius"), BorderLayout.WEST); p.add(jtf, BorderLayout.CENTER); jtf.setHorizontalAlignment(JTextField.RIGHT); setLayout(new BorderLayout()); add(p, BorderLayout.NORTH); add(new JScrollPane(jta), BorderLayout.CENTER); jtf.addActionListener(new TextFieldListener()); setTitle("Client"); setSize(500, 300); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setVisible(true); // It is necessary to show the frame here! try{ // Create a socket to connect to the server Socket socket = new Socket("localhost", 8000); // Socket socket = new Socket("130.254.204.36", 8000); // Socket socket = new Socket("drake.Armstrong.edu", 8000); // Create an input stream to receive data from the server toServer = new DataOutputStream(socket.getOutputStream()); } catch(IOException ex){ jta.append(ex.toString() + '\n'); } } private class TextFieldListener implements ActionListener{ public void actionPerformed(ActionEvent e){ try{ // Get the radius from the text field double radius = Double.parseDouble(jtf.getText().trim()); // Send the radius to the server toServer.writeDouble(radius); toServer.flush(); // Get area from the server double area = fromServer.readDouble(); //这一行为什么会报异常，但程序还能运行 // Display to the text area jta.append("Radius is " + radius + "\n"); jta.append("Area received from the server is " + area + '\n'); } catch(IOException ex){ System.err.println(ex); } } }}Server类
- Java code
package ex30;import java.io.*;import java.net.*;import java.awt.*;import java.awt.event.*;import javax.swing.*;public class Client extends JFrame{ // Text field for receiving radius private JTextField jtf = new JTextField(); // Text area to display contents private JTextArea jta = new JTextArea(); // IO streams private DataOutputStream toServer; private DataInputStream fromServer; public static void main(String[] args) { // TODO 自动生成方法存根 new Client(); } public Client(){ // Panel p to hold the label and text field JPanel p = new JPanel(); p.setLayout(new BorderLayout()); p.add(new JLabel("Enter radius"), BorderLayout.WEST); p.add(jtf, BorderLayout.CENTER); jtf.setHorizontalAlignment(JTextField.RIGHT); setLayout(new BorderLayout()); add(p, BorderLayout.NORTH); add(new JScrollPane(jta), BorderLayout.CENTER); jtf.addActionListener(new TextFieldListener()); setTitle("Client"); setSize(500, 300); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setVisible(true); // It is necessary to show the frame here! try{ // Create a socket to connect to the server Socket socket = new Socket("localhost", 8000); // Socket socket = new Socket("130.254.204.36", 8000); // Socket socket = new Socket("drake.Armstrong.edu", 8000); // Create an input stream to receive data from the server toServer = new DataOutputStream(socket.getOutputStream()); } catch(IOException ex){ jta.append(ex.toString() + '\n'); } } private class TextFieldListener implements ActionListener{ public void actionPerformed(ActionEvent e){ try{ // Get the radius from the text field double radius = Double.parseDouble(jtf.getText().trim()); // Send the radius to the server toServer.writeDouble(radius); toServer.flush(); // Get area from the server double area = fromServer.readDouble(); //这一行为什么会报异常，但程序还能运行 // Display to the text area jta.append("Radius is " + radius + "\n"); jta.append("Area received from the server is " + area + '\n'); } catch(IOException ex){ System.err.println(ex); } } }}
先运行，Server类，再运行client类，在Client中填入数字后，在Server类的第70行就报异常，
不知道为什么会这样，而且报异常后程序还能运行，就是一直报异常
[解决办法]
fromServer 未初始化
[解决办法]
在client个构造函数里面将fromServer初始化，即
- Java code
try{ // Create a socket to connect to the server Socket socket = new Socket("localhost", 8000); // Socket socket = new Socket("130.254.204.36", 8000); // Socket socket = new Socket("drake.Armstrong.edu", 8000); // Create an input stream to receive data from the server toServer = new DataOutputStream(socket.getOutputStream()); fromServer = new DataInputStream(socket.getInputStream()); } catch(IOException ex){ jta.append(ex.toString() + '\n'); }