为什么port是字符串而不是整数？

Question

The Port method returns a string and not an integer. What is the reason for that and is it safe to prefix the port with ":"?

Answer 1

This is because what appears after the colon can be either a port number or service name.

The following is a valid example where the service name is used instead of a port number:

listener, err := net.Listen("tcp", "localhost:https") // port 443
// ...

The port mapping for a particular service can be looked up using net.LookupPort. On Unix systems, the /etc/services file is sourced for the mappings.