用java编撰邮件收发程序

用java编写邮件收发程序
我想写一个邮件收发程序,不知道应该从那里入手,是不是要有个服务器啊,请各位前辈给点建议.我初学者,没有多少分,谢谢了.

[解决办法]
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.net.*;
import java.io.*;
import javax.swing.*;

/**
This program shows how to use sockets to send plain text
mail messages.
*/
public class MailTest
{
public static void main(String[] args)
{
JFrame frame = new MailTestFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

/**
The frame for the mail GUI.
*/
class MailTestFrame extends JFrame
{
public MailTestFrame()
{
setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
setTitle( "MailTest ");

setLayout(new GridBagLayout());

// we use the GBC convenience class of Core Java Volume 1 Chapter 9
add(new JLabel( "From: "), new GBC(0, 0).setFill(GBC.HORIZONTAL));

from = new JTextField(20);
add(from, new GBC(1, 0).setFill(GBC.HORIZONTAL).setWeight(100, 0));

add(new JLabel( "To: "), new GBC(0, 1).setFill(GBC.HORIZONTAL));

to = new JTextField(20);
add(to, new GBC(1, 1).setFill(GBC.HORIZONTAL).setWeight(100, 0));

add(new JLabel( "SMTP server: "), new GBC(0, 2).setFill(GBC.HORIZONTAL));

smtpServer = new JTextField(20);
add(smtpServer, new GBC(1, 2).setFill(GBC.HORIZONTAL).setWeight(100, 0));

message = new JTextArea();
add(new JScrollPane(message), new GBC(0, 3, 2, 1).setFill(GBC.BOTH).setWeight
(100, 100));

comm = new JTextArea();
add(new JScrollPane(comm), new GBC(0, 4, 2, 1).setFill(GBC.BOTH).setWeight(100,100));

JPanel buttonPanel = new JPanel();
add(buttonPanel, new GBC(0, 5, 2, 1));

JButton sendButton = new JButton( "Send ");
buttonPanel.add(sendButton);
sendButton.addActionListener(new
ActionListener()
{
public void actionPerformed(ActionEvent event)
{
new Thread(new
Runnable()
{
public void run()
{
comm.setText( " ");
sendMail();
}
}).start();
}
});
}

/**
Sends the mail message that has been authored in the GUI.
*/
public void sendMail()
{
try
{
Socket s = new Socket(smtpServer.getText(), 25);

InputStream inStream = s.getInputStream();
OutputStream outStream = s.getOutputStream();

in = new Scanner(inStream);
out = new PrintWriter(outStream, true /* autoFlush */);

String hostName = InetAddress.getLocalHost().getHostName();

receive();
send( "HELO " + hostName);
receive();
send( "MAIL FROM: < " + from.getText() + "> ");
receive();
send( "RCPT TO: < " + to.getText() + "> ");
receive();
send( "DATA ");
receive();
send(message.getText());
send( ". ");

receive();
s.close();
}
catch (IOException e)
{
comm.append( "Error: " + e);
}
}

/**
Sends a string to the socket and echoes it in the
comm text area.
@param s the string to send.
*/
public void send(String s) throws IOException
{
comm.append(s);
comm.append( "\n ");
out.print(s.replaceAll( "\n ", "\r\n "));
out.print( "\r\n ");
out.flush();
}

/**
Receives a string from the socket and displays it
in the comm text area.
*/
public void receive() throws IOException
{
if (in.hasNextLine());
{
String line = in.nextLine();
comm.append(line);
comm.append( "\n ");
}
}

private Scanner in;
private PrintWriter out;
private JTextField from;
private JTextField to;
private JTextField smtpServer;
private JTextArea message;
private JTextArea comm;

public static final int DEFAULT_WIDTH = 300;
public static final int DEFAULT_HEIGHT = 300;
}