go/src/net/port.go

// parsePort parses service as a decimal integer and returns the
// corresponding value as port. It is the caller's responsibility to
// parse service as a non-decimal integer when needsLookup is true.
//
// Some system resolvers will return a valid port number when given a number
// over 65536 (see https://golang.org/issues/11715). Alas, the parser
// can't bail early on numbers > 65536. Therefore reasonably large/small
// numbers are parsed in full and rejected if invalid.
func parsePort(service string) (port int, needsLookup bool) { … }