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Asked: 2026-06-12T15:30:21+00:00

Could anyone please help me create a simple, basic email client and email server

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Could anyone please help me create a simple, basic email client and email server using UDP and get familiar with how SMTP works?

I have just started computer networking and I only need to know the steps involved.

Thank you.

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1 Answer

  1. Editorial Team

    Internet RFCs (Request For Comments) are the best source for this kind of information: SMTP is outlined in RFC 821. The good news is that SMTP is a text-based protocol, just like HTTP and friends.

    Here’s an example dialogue between client C and server S (taken from wikipedia):

    S: 220 smtp.example.com ESMTP Postfix
C: HELO relay.example.org
S: 250 Hello relay.example.org, I am glad to meet you
C: MAIL FROM:<bob@example.org>
S: 250 Ok
C: RCPT TO:<alice@example.com>
S: 250 Ok
C: RCPT TO:<theboss@example.com>
S: 250 Ok
C: DATA
S: 354 End data with <CR><LF>.<CR><LF>
C: From: "Bob Example" <bob@example.org>
C: To: "Alice Example" <alice@example.com>
C: Cc: theboss@example.com
C: Date: Tue, 15 January 2008 16:02:43 -0500
C: Subject: Test message
C:
C: Hello Alice.
C: This is a test message with 5 header fields and 4 lines in the message body.
C: Your friend,
C: Bob
C: .
S: 250 Ok: queued as 12345
C: QUIT
S: 221 Bye
{The server closes the connection}

    Using UDP for email would not be the best idea, because UDP packets can be dropped. TCP would be better to use. But since you mention it’s an assignment, I guess it’s okay.

    So first write your generic UDP client/server code. Then modify it to support SMTP commands.

    I would start by implementing the simple echo protocol first. Or just search for some source code online in your favorite language for the echo protocol. For example, if you wanted to use C++ with boost.asio for networking, it has demo code for a UDP echo client and server. For Perl, there’s some simple UDP code here.

    Then skim over the parts of RFC 821 you need, and go from there. I’m guessing since it’s an assignment, you might not need everything in the protocol.

    Since the protocol is just simple text commands and responses, parsing it shouldn’t be a problem.

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