cr-launcher/src/utils.go

package main

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

func GetFreePort() (int, error) {
	addr, err := net.ResolveTCPAddr("tcp", "localhost:0")
	if err != nil {
		return 0, err
	}

	l, err := net.ListenTCP("tcp", addr)
	if err != nil {
		return 0, err
	}
	defer l.Close()
	return l.Addr().(*net.TCPAddr).Port, nil
}

func createPorts() (ws int, nport int, err error) {
	ws, err = GetFreePort()
	if err != nil {
		return
	}
	nport, err = GetFreePort()
	if err != nil {
		return
	}
	return
}

func GenHttpPort() (int, int, error) {

	portFile := path.Join(AppDataDir, "ports")
	portStr, err := os.ReadFile(portFile)
	if err == nil && len(portStr) > 0 {

		ports := strings.Split(string(portStr), "#")
		wsport, _ := strconv.Atoi(ports[0])
		nsport, _ := strconv.Atoi(ports[1])
		return wsport, nsport, nil
	}

	p1, p2, e := createPorts()
	if e != nil {
		return 0, 0, e
	}
	os.WriteFile(portFile, []byte(fmt.Sprintf("%d#%d", p1, p2)), os.ModePerm)
	return p1, p2, nil
}