Squid Cannot Bind Its Listener: Check the Address First
Separate a Squid listener bind failure from destination connectivity and inspect address-family availability in the actual process environment.
A bind error happens on the proxy host before the client can use the intended listener. Changing website URLs or proxy passwords will not make a nonexistent local address available.
Read the full failing endpoint: address, port, and address family. A message involving [::1] concerns IPv6 loopback. It is not the same as failing to connect outward to an IPv6 website.
Ask which network namespace owns it
For a containerized proxy, inspect the addresses available inside the container's network environment. IPv6 support and address configuration there can differ from the host. Publishing a container port does not automatically create every address that a service tries to bind.
Squid's listener reference explains that an explicit address binds a specific local endpoint. A hostname can introduce another source of confusion if it resolves to an address absent from that environment.
Other bind errors have different causes. An occupied port suggests another listener or instance. Permission denied may involve a privileged port or host security policy. An unavailable address points toward address configuration. Keep those observations distinct instead of treating every bind failure as a firewall rejection.
If the deployment is deliberately IPv4-only, choose an appropriate explicit IPv4 listener under the intended access policy. If IPv6 is required, configure that environment to support it. Binding publicly to a wildcard address merely to silence an error can expose the proxy more widely than intended.
Finally, check whether the failing socket is the client-facing HTTP listener or another Squid component. One warning does not prove every listener failed, but a working unrelated socket does not prove the endpoint clients need is available.