Node.js server fails to bind on ipv6 if ipv4 is not available

Start by reproducing the issue with the provided HTTP server and listen variants on Linux without TCPv4 support, then trace the server.listen networking path. Confirm the fix by verifying that an IPv6-only server becomes reachable and that the existing listen behavior remains correct in the relevant networking tests.

Version

v24.18.1

Platform

Linux ssh2 6.18.43-alwaysdata #1 SMP PREEMPT_DYNAMIC Fri Aug  7 07:39:43 UTC 2026 x86_64 GNU/Linux

Subsystem

No response

What steps will reproduce the bug?

1. Run a HTTP server (code below)
2. Try to connect to it (via e.g. python, netcat, a browser etc.)

code:

const http = require("http");
const server = http.createServer((req,res)=>{
     res.writeHead(200, "Content-Type", "text/plain");
     res.write("ok");
     res.end();
});

server.listen({ port: 8300 }, ()=> {
    console.log("Server is running");
});

I also tried all the following:

server.listen({ port: 8300, host: "::" }, ()=> {
    console.log("Server is running");
});

server.listen({ port: 8300, host: "::", ipv6Only: true }, ()=> {
    console.log("Server is running");
});

server.listen({ port: 8300, host: "", ipv6Only: true }, ()=> {
    console.log("Server is running");
});

server.listen({ port: 8300, host: "0.0.0.0", ipv6Only: true }, ()=> {
    console.log("Server is running");
});

server.listen({ port: 8300, host: "::1", ipv6Only: true }, ()=> {
    console.log("Server is running");
});

server.listen({ port: 8300, host: "" }, ()=> {
    console.log("Server is running");
});

server.listen(8300, "::", ()=> {
    console.log("Server is running");
});

server.listen(8300, "", ()=> {
    console.log("Server is running");
});

// maybe even more i forgot

How often does it reproduce? Is there a required condition?

TCPv4 must not be available on the OS.
For example, netstat -lntp must say this:

netstat: no support for `AF INET (tcp)' on this system.

netstat -lntp6 must not say that, however - instead, it should succeed:

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name

What is the expected behavior? Why is that the expected behavior?

The server should be accessible

What do you see instead?

No error is thrown or logged, however, I cannot connect to the server in any imaginable way

Additional information

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