smtpclientdemo.java

FetchURL.java 连接指定URL

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


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();
	}
}