func (a TCPPort) String() string {
	if name, ok := TCPPortNames[a]; ok {
		return fmt.Sprintf("%d(%s)", a, name)
	}
	return strconv.Itoa(int(a))
}
{TCP,UDP,SCTP}PortNames can be found in iana_ports.go
String returns the port as "number(name)" if there's a well-known port name,
or just "number" if there isn't.  Well-known names are stored in
TCPPortNames.
package layers
import (
	"fmt"
	"strconv"
	"github.com/google/gopacket"
)
type TCPPort uint16
type UDPPort uint16
type RUDPPort uint8
type SCTPPort uint16
type UDPLitePort uint16
var RUDPPortNames = map[RUDPPort]string{}
var UDPLitePortNames = map[UDPLitePort]string{}