SMTP Connecting

[S Hayes]

Using the code below, I can't connect to any MX servers that I find with nsloookup -type=MX. I don't think the ports are blocked though, since I can use Thunderbird with my Gmail account. Any suggestions?

package my_mailer;
 
import java.io.*;
import java.net.*;
import java.util.*;
import java.text.*;
 
//code borrowed from <a href="http://www.developerfusion.co.uk/show/1975/" target="_blank" rel="nofollow">http://www.developerfusion.co.uk/show/1975/</a>
public class CMDMailer
{
private String m_sHostName;
private int m_iPort;
private Socket smtpSocket = null;
private BufferedWriter bw = null;
private BufferedReader br = null;
private BufferedReader cmdLn = new BufferedReader(new InputStreamReader(System.in));

public static void main(String args[])
{
CMDMailer cmdM = new CMDMailer(args[0], args[1]);
}

public CMDMailer(String m_sHostName, String m_iPort)
{
this.m_sHostName = m_sHostName;
this.m_iPort = Integer.parseInt(m_iPort);
startSession();
}

public void startSession()
{
Date dDate = new Date();
DateFormat dFormat = DateFormat.getDateInstance(DateFormat.FULL,Locale.US);

try
{
// Open port to server
smtpSocket = new Socket(m_sHostName, m_iPort);
bw = new BufferedWriter(new OutputStreamWriter(smtpSocket.getOutputStream()));
br = new BufferedReader(new InputStreamReader(smtpSocket.getInputStream()));
            
if(smtpSocket != null && bw != null && br != null)
{
// Connection was made. Socket is ready for use.
try
{
String s = null;
String c = null;
while(true)
{
s = read();
c = readCMDLn();
write(c);
if(c.toLowerCase().indexOf("exit") >= 0)
{
break;
}
}
log("Session Ended");
close();
}
catch(Exception e)
{
log("Cannot send email as an error occurred.");
}
}
}
catch(Exception e)
{
log("Host " + m_sHostName + " unknown");
}
}

private String read()
{
String s = null;
try
{
s = br.readLine();
}
catch(IOException ex)
{
log(ex.toString());
}
log("S: " + s);
return s;
}

private void write(String s)
{
try
{
bw.write(s + "\r\n");
bw.flush();
}
catch(IOException ex)
{
log(ex.toString());
}
}

private String readCMDLn()
{
String s = null;
try
{
System.out.print("C: ");
s = cmdLn.readLine();
}
catch(IOException ex)
{
log(ex.toString());
}
return s;
}

protected void log(String s)
{
System.out.println(s);
}

protected void close()
{
try
{
if(bw != null)
{
bw.close();
}
if(br != null)
{
br.close();
}
if(smtpSocket != null)
{
smtpSocket.close();
}
System.exit(0);
}
catch(IOException ex)
{
log(ex.toString());
}

}
}

[Van Glass]

Gmail uses a secure SSL POP/SMTP connections that aren't blocked by ISP's. It may be that your ISP is only allowing you connections to it's own SMTP server and no others ... this is to prevent spam.

To verify try connecting manually to one of the MX hosts using telnet command:


e.g.

telnet hostname 25

If you get a response your ok. Otherwise your ISP is blocking you.