[Bug]: opencode serve does not release port on exit — zombie self-loopback connection locks LISTENING socket (Windows) #32932

Description

When opencode serve exits or crashes, the server port (e.g. 4096) is not released. A self-loopback TCP connection (127.0.0.1:54420 ↔ 127.0.0.1:4096, both endpoints owned by the now-dead server PID) remains in ESTABLISHED state, keeping the LISTENING socket locked. On Windows, this port cannot be reclaimed by a new opencode serve --port 4096 invocation — it fails with ServeError: Unexpected error.

The dead process (PID 19152) no longer exists in the process table, but the Windows kernel TCP stack keeps the socket open because the self-loopback ESTABLISHED connection never receives a FIN/RST from either end. All other client connections are stuck in CLOSE_WAIT, also waiting on this zombie self-connection.

This is related to #22198 (SSE connections stuck in CLOSE_WAIT) but is a distinct issue: the root cause here is that opencode serve does not perform graceful socket shutdown on exit, leaving a self-loopback connection that locks the listening port indefinitely on Windows.

Evidence

1. ServeError on restart: opencode serve --port 4096 → Error: Unexpected error / ServeError
2. Dead PID still holds LISTENING: netstat -ano shows LISTENING 127.0.0.1:4096 PID 19152, but tasklist /fi "pid eq 19152" → "No tasks running which match the specified criteria"
3. Self-loopback ESTABLISHED: netstat -ano shows 127.0.0.1:54420 ↔ 127.0.0.1:4096 ESTABLISHED PID 19152 on both sides — a connection from the server to itself that was never closed
4. 54+ CLOSE_WAIT connections: All other connections to port 4096 are in CLOSE_WAIT, waiting on the zombie self-connection
5. Port never releases: Killed all OpenCode Desktop processes, killed all Edge browser processes, waited several minutes — port 4096 still held by dead PID 19152. Only a full OS reboot clears it.

Steps to reproduce

1. Start opencode serve --port 4096 (WSL2 or Windows)
2. Open OpenCode Desktop and connect it to the server (this creates SSE connections including self-loopback)
3. Kill the opencode serve process (e.g. close the terminal, or the process crashes)
4. Attempt to restart: opencode serve --port 4096 → ServeError: Unexpected error
5. Verify with netstat -ano | findstr 4096: LISTENING socket still held by dead PID, with a self-loopback ESTABLISHED connection

Expected behavior

opencode serve should perform graceful shutdown on exit:

• Close all SSE streams and send FIN to connected clients
• Close the self-loopback connection (if any)
• Close the LISTENING socket
• The port should be immediately available for a new instance

Suggested fix

1. Register a process exit handler (process.on('exit'), process.on('SIGTERM'), process.on('SIGINT')) that calls server.close() and closes all active connections
2. On Windows, also call server.removeAllListeners() and explicitly destroy sockets that are in CLOSE_WAIT
3. Consider adding a TCP keepalive/idle timeout on SSE connections so zombie connections eventually self-close even if the server process dies ungracefully

Plugins

oh-my-openagent

OpenCode version

OpenCode Desktop v1.17.8 / opencode-web (latest)

Operating System

Windows 11 (WSL2, Ubuntu 24.04)

Terminal

Windows Terminal / PowerShell