Sending smtp email from microcontroller

Question

This may not be in the right location, so tell me and I'll move it.

I am a recent EE grad and I was hired to build a system that exists on a SoC with a simple 32-bit processor. The system basically monitors several external devices and performs some DSP on it, and then is supposed to send the results using a WiFi device (in my case I have the ESP8266 using UDP) to an email server for logging/notification.

I have been trying to find a library that I can use, but my uC can only program in C and I have it set up for UDP, and everything is in C++ using some other protocol, or something else completely.

I am great at DSP, decent at SoC's and uC's, but when it come to this email server communication thing I am at a loss.

I have successfully configured everything for the sensors, the datapath, the DSP, and connected the system to my WiFi via UDP, but I have yet to figure out how to send data to any servers.

Could someone help me understand how I should go about this?

I have looked into some simple SMTP commands such as HELO, MAIL, RCPT, DATA, etc. but I cannot understand how I actually should implement them in my code.

When I send out the WiFi data via UDP what type of data do I send and how do I format it? Do I need to send any other kind of flags? How should I expect the response? I also know the data has to be transformed into base 64 which is confusing me further.

I am also not super familiar with UDP to begin with, I have been using libraries that are part of the SoC's default library to connect to my WiFi.

I know these may either seem like obvious or stupid questions but it is were I no longer have any knowledge, and everything I find online doesn't make sense, or doesn't attempt to explain it, just gives a pre-made solution

I have found the RFC2821 but it doesn't get any clearer.

I know that's a lot but any help at all would be a lifesaver!

Answer 1

Since you are asking this question, I'm assuming that you are not booting and running an OS suitable for micro-controllers such as an embedded variant of Linux or such. If you were, you would simply be able to take advantage of possibly built in applications or other existing code.

But you don't mention having written an Ethernet stack, so are you using some other library or operating environment which might have some of the functionality needed for an implementation of SMTP?

If you don't and really do need to write your own SMTP client to run directly on the processor you are using, then you should be able to find plenty of examples of source code for this. A quick google search of How To Write an SMTP client showed a few articles with some example code. One article seems to be an exact hit, but you need to look at it further.

However, I would highly suggest just sitting down with a telnet client and connect to an SMTP server you are allowed to use and try the commands you need to just send a message. If you only need to send text, you don't need to get involved in MIME encoding or anything like that.