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how do i get TcpListener to accept multiple connections and work with each one individually?

Posted on 2011-03-17
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Last Modified: 2012-05-11
i have an smtp listener that works well but is only able to receive one connection. My c# code is below and i am running it as a service. My goal is to have it runnign on a server and parsing multiple smtp messages sent to it.

currently it parses the first message and stops working. how can i get it to accept the 2nd, 3rd, 4th... smtp message and process it like it does the first?

here is my code:

 
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.Sockets;
using System.Net;
using System.IO;  

  

namespace SMTP_Listener
{
    class Program
    {
        static void Main(string[] args)
        {


            TcpListener listener = new TcpListener(IPAddress.Any , 8000);
            TcpClient client;
            NetworkStream ns;

            listener.Start();

            Console.WriteLine("Awaiting connection...");
            client = listener.AcceptTcpClient();
            Console.WriteLine("Connection accepted!");

            ns = client.GetStream();

            using (StreamWriter writer = new StreamWriter(ns))
            {
                writer.WriteLine("220 localhost SMTP server ready.");
                writer.Flush();

                using (StreamReader reader = new StreamReader(ns))
                {
                    string response = reader.ReadLine();

                    if (!response.StartsWith("HELO") && !response.StartsWith("EHLO"))
                    {
                        writer.WriteLine("500 UNKNOWN COMMAND");
                        writer.Flush();
                        ns.Close();
                        return;
                    }

                    string remote = response.Replace("HELO", string.Empty).Replace("EHLO", string.Empty).Trim();

                    writer.WriteLine("250 localhost Hello " + remote);
                    writer.Flush();

                    response = reader.ReadLine();

                    if (!response.StartsWith("MAIL FROM:"))
                    {
                        writer.WriteLine("500 UNKNOWN COMMAND");
                        writer.Flush();
                        ns.Close();
                        return;
                    }

                    remote = response.Replace("RCPT TO:", string.Empty).Trim();
                    writer.WriteLine("250 " + remote + " I like that guy too!");
                    writer.Flush();

                    response = reader.ReadLine();

                    if (!response.StartsWith("RCPT TO:"))
                    {
                        writer.WriteLine("500 UNKNOWN COMMAND");
                        writer.Flush();
                        ns.Close();
                        return;
                    }

                    remote = response.Replace("MAIL FROM:", string.Empty).Trim();
                    writer.WriteLine("250 " + remote + " I like that guy!");
                    writer.Flush();

                    response = reader.ReadLine();

                    if (response.Trim() != "DATA")
                    {
                        writer.WriteLine("500 UNKNOWN COMMAND");
                        writer.Flush();
                        ns.Close();
                        return;
                    }

                    writer.WriteLine("354 Enter message. When finished, enter \".\" on a line by itself");
                    writer.Flush();

                    int counter = 0;
                    StringBuilder message = new StringBuilder();

                    while ((response = reader.ReadLine().Trim()) != ".")
                    {
                        message.AppendLine(response);
                        counter++;

                        if (counter == 1000000)
                        {
                            ns.Close();
                            return;  // Seriously? 1 million lines in a message?
                        }
                    }

                    writer.WriteLine("250 OK");
                    writer.Flush();
                    ns.Close();
                    // Insert "message" into DB
                    Console.WriteLine("Received message:");
                    Console.WriteLine(message.ToString());
                }
            }

            Console.ReadKey();



        }
    }
}

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Question by:realcoding
  • 3
4 Comments
 
LVL 11

Expert Comment

by:wrmichael
ID: 35156717
You have to make it multi-threaded.

I have a book with that as an example.
 
I'll find the title for you.
0
 
LVL 11

Accepted Solution

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wrmichael earned 500 total points
ID: 35156724
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LVL 11

Expert Comment

by:wrmichael
ID: 35156737
I think this was the book:

http://oreilly.com/catalog/9780596001179 

it is at home. If the sample doesn't help I'll pull it out late tonight and find the sample code in it.
0
 

Author Comment

by:realcoding
ID: 35158422
@wrmichael: the C# sample will do just fine thanks. I think i can run with that.
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