Does an open TCP socket connection consume data when not used?

Question

I have a TCP socket connection established between my server and a modem which has a active GSM module and sim card installed.

I create this wirless 3G connection via socat:

/usr/bin/socat open:/dev/ttyVA8500,nonblock,echo=0,raw TCP-LISTEN:8500,reuseaddr,fork

This little command listens for TCP connections on port 8500 and writes the data into the virtual serial port /dev/ttyVA8500. Now when I write to the virtual serial port on my server the data will be send to the modem which then will send a response.

This communication costs traffic. I can see this traffic in the monitoring tool of the GSM provider.

Problem

I can see data consumption in the GSM monitoring even when I am not talking to the modem. It's far less, about 2 kiB per hour. But I have a limit of 1 MB per month. So my questions is where does this "ghost" 3G data consumption come from? Does the TCP socket connection itself cost traffic to keep it alive??

While I was not talking to the TCP connection I used a tcp sniffer to check for ghost traffic:

sudo tcpflow -i any -C -e port 8502

However this did not show any traffic (when I started communication again it listed all data just fine;)).

Answer 1

no when you are not talking to server it wont gona take any data however the gsm module that your are attaching have to maintain the connection or keep the connection alive because of which it have to send signal of keeping alive the connection after every few seconds you can improve it by disconnecting the data and only enable it when you gona start talking to server