Using the WebSockets library for the GSM SIM800 modem

[Djaison]

Hello! I'm using the wonderful library arduinoWebSockets on ESP32. I want to use a GSM modem to connect my client running on ESP32 with a remote server via Websocket. The SIM800 modem has its own TCP / IP stack and involves working with AT commands. But this mode of operation does not fit.
However, it can be switched to point to point over serial (PPPoS) mode. I'd like to use the TCP Arduino stack with the WebSockets library. Question: Is it possible to connect a websockets connection to a serial interface as the simplest solution? Or do I need to write the TCP Client and Server class for the SIM800 and then include them in the arduino WebSockets library? (I'm new to C ++ (6 months +))

P.S. It would be nice if @Links2004 pays attention to my question :-)
Thank you in advance!

[Links2004]

Hi,

the code require a Arduino Client or Server class,
you can program the class to send all data via serial,
not sure how the PPPoS protocol is looking like.
but all you need is a abstraction layer with the arduino client class Interface.
a simply TCP to Serial via abstraction layer is easy done, but the question is if the PPPoS protocol is requiring additional stuff.

if you have this kind of Abstraktion the rest is easy.
simply set the defines to your class, like its done for different TCP stack here:
https://github.com/Links2004/arduinoWebSockets/blob/master/src/WebSockets.h#L148-L164

[Djaison]

I assumed that I would have to create a Client class (I'm using the websocket client). If I understand correctly, to create such a Class, I need to properly configure lwiP PPPoS and use the standard API library lwIP in my class Arduino Client GSM?

[Links2004]

you are not forced to use lwiP but it one way to do it.
you need to implement the Client class:

https://www.arduino.cc/en/Reference/ClientConstructor
https://github.com/esp8266/Arduino/blob/master/cores/esp8266/Client.h

[Djaison]

Thanks for the quick answers! But somehow the functionality of PPPoS is laid in lwIP? If I understand correctly in my Client class, I need to configure PPPoS and through this channel send a raw TCP stream on top of which is the websocket.
Or is it enough for me in my class ClientGSM to inherit from the base class arduino Client.h and override in it such methods as: read (); and write (); to output to Serial?

[Links2004]

you only need to wirte a ClientGSM, the class need to send all commands to your GSM module via serial that are needed to open the TCP socket and read and write to it.

I have no glue on how complexe PPPoS is but it need to be handled in the ClientGSM.
if your class is offloading some of the protocol work to lwIP or not is up to you.

if you implement all the functions for the client class it will work fine.
this is how all the different Arduino network stacks are working.

if its fully integrated in to lwIP you may only need to register the GSM modem as new interface in to lwIP.
then you not need any class, since the WiFiClient class basically is a lWIP client class its not bound to WiFi ;)

[imranaalam]

Any progress on your side?

Any progress ?

[ehsan9ir]

Hi
Didn't you find a solution to this problem after all these years to support the web socket on sim800? @Djaison

[Djaison]

Hello. Yes, I was able to use websocket using sim800 modem. I did not use PPPoS mode, but used the internal TCP stack of the GSM modem. As Marcus said, it is enough to implement your Client class, in which you implement all the methods of this class. Initialize the modem and establish a permanent TCP connection to the server. Your payload messages, along with the websocket protocol headers, are simply passed as TCP stack messages

[ekadesign]

@Djaison could you publish implementation ?

[Miftakhunnurudin]

Hey bro could you publish the final result?

[Sandi2211]

@Djaison I'm also interested. Would be great if you could share the code mate.

[WTHfloyd]

Hi @Djaison - Yes if you could share code on how you did this - huge thanks!

[re-vax]

Hi there!
I'm also playing around SIM800 on ESP32. It would be nice to have a working stack to use SIMM800 as a modem.
Please share, even if it's not production ready ;)