smtpclientdemo.java

Java网络编程与分布式计算, 主要分析java网络各方面的编程, 提供许多实用安全

import java.io.*;
import java.net.*;
import java.util.*;

// Chapter 8, Listing 1
public class SMTPClientDemo
{
  protected int port = 25;
  protected String hostname = "localhost";
  protected String from = "";
  protected String to = "";
  protected String subject = "";
  protected String body = "";

  protected Socket socket;
  protected BufferedReader br;
  protected PrintWriter pw;

  // Constructs a new instance of the SMTP Client
  public SMTPClientDemo() throws Exception
  {
	try
	{
		getInput();
		sendEmail();
	}
	catch (Exception e)
	{
		System.out.println ("Error sending message - " + e);
	}
  }

  public static void main(String[] args) throws Exception
  {
	  // Start the SMTP client, so it can send messages
	  SMTPClientDemo client = new SMTPClientDemo();
  }

  // Check the SMTP response code for an error message
  protected int readResponseCode() throws Exception
  {
    String line = br.readLine();
    System.out.println("< "+line);
    line = line.substring(0,line.indexOf(" "));
    return Integer.parseInt(line);
  }

  // Write a protocol message both to the network socket and to the screen
  protected void writeMsg(String msg) throws Exception
  {
    pw.println(msg);
    pw.flush();
    System.out.println("> "+msg);
  }

  // Close all readers, streams and sockets
  protected void closeConnection() throws Exception
  {
    pw.flush();
    pw.close();
    br.close();
    socket.close();
  }

  // Send the QUIT protocol message, and terminate connection
  protected void sendQuit() throws Exception
  {
    System.out.println("Sending QUIT");
    writeMsg("QUIT");
    readResponseCode();

    System.out.println("Closing Connection");
    closeConnection();
  }

  // Send an email message via SMTP, adhering to the protocol known as RFC 2821
  protected void sendEmail() throws Exception
  {
    System.out.println("Sending message now: Debug below");
    System.out.println("--------------------------------------------------------------");

    System.out.println("Opening Socket");
    socket = new Socket(this.hostname,this.port);

    System.out.println("Creating Reader & Writer");
    br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
    pw = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()));

    System.out.println("Reading first line");
    int code = readResponseCode();
    if(code != 220) { socket.close(); throw new Exception("Invalid SMTP Server"); }

    System.out.println("Sending helo command");
    writeMsg("HELO "+InetAddress.getLocalHost().getHostName());
    code = readResponseCode();
    if(code != 250)
    {
      sendQuit();
      throw new Exception("Invalid SMTP Server");
    }

    System.out.println("Sending mail from command");
    writeMsg("MAIL FROM:<"+this.from+">");
    code = readResponseCode();
    if(code != 250)
    {
      sendQuit();
      throw new Exception("Invalid from address");
    }

    System.out.println("Sending rcpt to command");
    writeMsg("RCPT TO:<"+this.to+">");
    code = readResponseCode();
    if(code != 250)
    {
      sendQuit();
      throw new Exception("Invalid to address");
    }

    System.out.println("Sending data command");
    writeMsg("DATA");
    code = readResponseCode();
    if(code != 354)
    {
      sendQuit();
      throw new Exception("Data entry not accepted");
    }

    System.out.println("Sending message");
    writeMsg("Subject: "+this.subject);
	writeMsg("To: "+this.to);
	writeMsg("From: "+this.from);
    writeMsg("");
    writeMsg(body);
    code = readResponseCode();
    sendQuit();
    if(code != 250)
      throw new Exception("Message may not have been sent correctly");
    else
      System.out.println("Message sent");
  }

  // Obtain input from the user
  protected void getInput() throws Exception
  {
	// Read input from user console
    String data=null;
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

	// Request hostname for SMTP server
    System.out.print("Please enter SMTP server hostname: ");
    data = br.readLine();
    if (data == null || data.equals("")) hostname="localhost";
    else 
		hostname=data;    

	// Request the sender's email address
	System.out.print("Please enter FROM email address: ");
	data = br.readLine();
	from = data;

	// Request the recipient's email address
    System.out.print("Please enter TO email address :");
    data = br.readLine();
    if(!(data == null || data.equals("")))
		to=data;

    System.out.print("Please enter subject: ");
    data = br.readLine();
		subject=data;

    System.out.println("Please enter plain-text message ('.' character on a blank line signals end of message):");
    StringBuffer buffer = new StringBuffer();

	// Read until user enters a . on a blank line
    String line = br.readLine();
    while(line != null)
    {
	  // Check for a '.', and only a '.', on a line
      if(line.equalsIgnoreCase("."))
      {
        break;
      }
      buffer.append(line);
      buffer.append("\n");
      line = br.readLine();
    }
    buffer.append(".\n");
    body = buffer.toString();
  }
}