Connection reset by peer despite using --stay-alive

[parski]

First of all, forgive my ignorance on TCP.

I use tcptunnel to proxy traffic from one PC to another on my LAN that is connected to a VPN to piggyback off that VPN connection. I route two tunnels: HTTP and git over ssh and it works remarkably well. Until it doesn't.

Seemingly spontaneously the connection will break and I will have to reset it. Sometimes it won't do this for hours and other times it happens every few minutes. This is the Mac version of tcptunnel installed via Homebrew on an Apple Silicon machine.

The output is always the following:

use_tunnel: recv(rc.client_socket): Connection reset by peer

I route the HTTP traffic by starting the tunnel like this:

// VPN connected machine LAN IP = 1.2.3.4
// IP of machine only accessible with VPN = 4.3.2.1
$ sudo tcptunnel --bind-address=1.2.3.4 --local-port=443 --remote-host=4.3.2.1 --remote-port=443 --stay-alive &

Same thing with different ports for git over ssh.

I thought the --stay-alive argument would prevent this from happening but evidently it does not.

Is it obvious to somebody what I am doing wrong?