detect new container port listeners, automatically forward from host #47

banksean · 2025-05-02T01:00:28Z

rough outline:

innie process runs "netstat -lntu" in a polling loop to monitor port listeners inside the container
if a new port listener appears (or old one disappears), innie posts a message to outie with the port number (maybe some other info?)
when outie gets a "/port-listner-changed" event from innie, it shells out to "ssh -L hostPort:127.0.0.1:containerPort" to start tunneling over ssh, and updates the UI to let the user know about the newly tunneled port.

At least one gotcha to consider: we might not always (or even usually?) be able to make hostPort == containerPort

e.g.: app inside container starts with -p 8080 so it prints out "visit http://localhost:8080" to the terminal
innie netstat poller picks up the new listener on 8080, POSTs to outie about it
outie gets the new-port-listener msg, however: 8080 is already taken on host by some other process
outie assigns a different port than the one requested by the innie, say 8081: "ssh -L 8081:127.0.0.1:8080"
...confusion ensues when you click on the "visit http://localhost:8080" message from the container and do not get the app that printed that message

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