TCP Server Socket: Fast switch back to AT-Mode


I’m new at this topic and I’m using a WISMO228.
My application is used to answer to requests over TCP/IP from several clients “on the other side of the internet”.

On WISMO, I want to create a TCP-Server with more than one socket with the following behaviour:
When I receive data on the first socket (e.g. +WIPDATA: 2,1,12), I switch to data mode (AT+WIPDATA=2,1,2) and exchange data (receive question, send answer) on this socket.
After this I will switch back to AT mode as fast as possible to listen for data on the other sockets.

Is there a possibility to switch back faster than with the “+++” methode?
I have not the time to spend 1second to guarantee the guard time.
And WISMO228 has not “another UART” to send AT+WIPDATA=,,0 to switch back like it’s written in the document “WISMO 228 TCP/IP AT Commands Manual”, p.48 :frowning:

Please consider: I will not close the connectoin on the first socket! I will just switch back to AT mode.

Thank you for your help!



Use the virtual ports.
Look for information about the command AT+CMUX.

The Multiplexer mode enables one serial interface to transmit data to N-different customer
applications. This is achieved with the Multiplexer (Mux) that provides N-virtual channels.

In Multiplexer mode, AT commands and data are encapsulated into packets. Each packet has channel
identification and may vary in length.

“Multiplexer Protocol”; ETSI TS 101 369 V7.1.0 (1999-11), GSM 07.10 Version 7.1.0,
Release 199


Many thanks for your hint.

I found some information about the CMUX feature in the document “WM_DEV_AT_APN_003_004.pdf”.
But I’m wondering, because in the document above, WISMO228 is not listed as compatible hardware.

Even so, WISMO answer to the command AT+CMUX, and I’ll try it…


free sources GSM 07.10