Zeabur Port Mismatch

Name: zeabur-port-mismatch
Rating: 92
Author: zeabur

Symptom

code

dial tcp 10.x.x.x:3000: i/o timeout
dial tcp 10.x.x.x:80: connection refused

Cause

Proxy expects service on port X, but service listens on port Y.

Diagnose

•Check what port proxy expects (from Caddyfile/nginx.conf)
•Check what port container exposes (Dockerfile EXPOSE)

Common Mismatches

Proxy expects	Container has	Fix
`:3000`	nginx default `:80`	Change template port to 80
`:80`	app on `:3000`	Change template port to 3000

Fix in Template

yaml

ports:
  - id: web
    port: 3000  # Match what container actually exposes
    type: HTTP

Check official Dockerfile for EXPOSE directive.

Headless Service (502 with no listener)

Symptom

Service is running (no crash), but proxy returns 502 Bad Gateway permanently.

Cause

Service does not listen on any HTTP port. Examples: chatbot gateways, background workers, message queue consumers. The template declares an HTTP port but nothing binds to it.

Fix

Add a lightweight HTTP health check server that runs in the background alongside the main process:

bash

# Start before main process in startup script
# IMPORTANT: port must match spec.ports[].port in your template
python3 -c "
from http.server import HTTPServer, BaseHTTPRequestHandler
import json
class H(BaseHTTPRequestHandler):
    def do_GET(self):
        self.send_response(200)
        self.send_header('Content-Type','application/json')
        self.end_headers()
        self.wfile.write(json.dumps({'status':'ok'}).encode())
    def log_message(self,*a): pass
HTTPServer(('0.0.0.0', 8080), H).serve_forever()
" &
exec my-headless-app