fails:TCPServer#listen using IPv4 raises when the given argument can't be coerced to a Fixnum
fails:TCPServer#listen using IPv6 raises when the given argument can't be coerced to a Fixnum
fails:TCPServer#listen using IPv4 raises when the given argument can't be coerced to an Integer
fails:TCPServer#listen using IPv6 raises when the given argument can't be coerced to an Integer
