Fixing port conflicts and CORS problems

Is the server up but you cannot connect, or does the browser (connect-web) show a CORS error? Checking the port settings and the origin configuration together solves most cases.

Symptoms

• The server reports that the port is already in use at startup.
• The client cannot connect to the server.
• A CORS (Cross-Origin) error appears in the browser console.

Causes

First, let's go over Bareun's port layout.

Solution

1. Check for a port conflict first. If the startup error says "port in use," another process is using the same port. Change address.port in bareun.json (default 5656) to a free port and run the server again.

   Copy

   {
     "address": { "ipAddr": "0.0.0.0", "port": 5656 },
     "staticAddress": { "ipAddr": "0.0.0.0", "port": 5656 }
   }
   

   A restart is needed after changing the port

   A port change takes effect only after you run the server again. Also match the port the client requests.

2. Check that the client connects to the right port. Both the native installation and the Docker distribution use the default 5656 port (the native installation can also use 5658). Check that you are sending requests to the port that fits your environment.

3. For browsers (connect-web), check CORS. The Bareun server (connect-go) accepts connect-web requests directly and handles CORS itself. No separate proxy is needed. If the web frontend sends requests from an origin different from the server's, check that the server is configured to allow that origin and that the client requests the correct address and port.

Prevention and tips

• If you run several instances on one host, plan ahead so the ports do not overlap.
• For a setup connected from a browser, you can call the server directly with connect-web. Serving from the same origin or matching the server's allowed-origin setting avoids CORS problems.

Frequently asked questions

Q. How do I change the port if there is a conflict?

Change address.port in bareun.json (default 5656) to a free port and run the server again. If you serve static resources on the same port, it is also good to match staticAddress.port.

Q. I get a CORS error in the browser.

If you send requests from a different origin with connect-web, CORS handling is needed. The Bareun server handles connect-web and CORS itself, so check that the server is configured to allow that origin and that the client requests the correct address and port. If you serve from the same origin, CORS problems do not arise at all.

Q. Are the native and Docker ports the same?

Yes. Both use the default 5656 port. The native installation serves gRPC/Connect and static resources on the same port (or 5658), and the Docker distribution also serves directly on 5656. The Bareun server (connect-go) handles gRPC, connect-web, and HTTP+JSON all on one port and takes care of CORS itself, so a separate Envoy frontend (formerly 5757) and the admin port 9902 are not used.

Q. What is the path when calling with REST (HTTP+JSON)?

Bareun uses Connect paths. Call it in the form POST /bareun.<Service>/<Method> (for example, POST /bareun.LanguageService/AnalyzeSyntax). The old gateway path (/bareun/api/v1/...) is not used. It is handled on the same 5656 port together with gRPC and connect-web.