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

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

edit: offensive comment removed by moderator

Beginne damit, das Problem mit dem bereitgestellten HTTP-Server und den listen-Varianten unter Linux ohne TCPv4-Unterstützung zu reproduzieren, und verfolge anschließend den Netzwerkpfad von server.listen. Bestätige die Behebung, indem du überprüfst, dass ein IPv6-only-Server erreichbar wird und dass das bestehende listen-Verhalten in den relevanten Netzwerktests weiterhin korrekt ist.