You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: nat.go
    path of file: ./repos/faasd/vendor/github.com/docker/go-connections/nat
    
    the code of the file until where you have to start completion: // Package nat is a convenience package for manipulation of strings describing network ports.
package nat

import (
	"fmt"
	"net"
	"strconv"
	"strings"
)

const (
	// portSpecTemplate is the expected format for port specifica
    
func SplitProtoPort(rawPort string) (string, string) {
	parts := strings.Split(rawPort, "/")
	l := len(parts)
	if len(rawPort) == 0 || l == 0 || len(parts[0]) == 0 {
		return "", ""
	}
	if l == 1 {
		return "tcp", rawPort
	}
	if len(parts[1]) == 0 {
		return "tcp", parts[0]
	}
	return parts[1], parts[0]
}