catsync/main.go

package main

import (
	"code.uocat.com/tqcq/catsync/pb"
	"context"
	"fmt"
	"google.golang.org/protobuf/proto"
	"google.golang.org/protobuf/types/known/timestamppb"
	"net"
	"sync"
	"time"
)

var (
	PeerList = make(map[string]net.UDPAddr)
)

func LANServer(ctx context.Context, conn *net.UDPConn) {

	var wait_group sync.WaitGroup
	defer wait_group.Wait()
	for {
		buf := make([]byte, 1024)
		n, remote_addr, err := conn.ReadFromUDP(buf)
		if err != nil {
			fmt.Printf("Recv failed. %v\n", err)
			continue
		}
		if n != 0 {
			// process request
			wait_group.Add(1)
			go func() {
				defer wait_group.Done()

				fmt.Printf("remote_addr: %s\n", remote_addr.AddrPort().String())
				pm := &pb.PeerMessage{}
				err := proto.Unmarshal(buf[:n], pm)
				if err != nil {
					fmt.Printf("Unmarshal failed. %v\n", err)
					return
				}

				fmt.Printf("uid: %s, send_timestamp: %s\n", pm.Uid, pm.SendTimestamp.AsTime().Local())
			}()
			continue
		}
	}
}

func LANClient(ctx context.Context, conn *net.UDPConn) {
	broadcast_addr, err := net.ResolveUDPAddr("udp4", "255.255.255.255:8829")
	if err != nil {
		fmt.Printf("err: %v", err)
		return
	}

	for {
		pm := &pb.PeerMessage{
			MagicNumber:   13,
			Version:       0,
			SendTimestamp: timestamppb.Now(),
			Type:          pb.PeerMessageType_PEER_MESSAGE_TYPE_REQUEST,
			Uid:           "test uid",
		}
		buf, err := proto.Marshal(pm)
		if err != nil {
			fmt.Printf("err: %v\n", err)
		} else {
			_, _ = conn.WriteToUDP(buf, broadcast_addr)
		}
		time.Sleep(5 * time.Second)
	}
}

func main() {
	listenAddr, err := net.ResolveUDPAddr("udp4", ":8829")
	if err != nil {
		fmt.Printf("ResolveUDPAddr failed. %v\n", err)
		return
	}
	broadcastServer, err := net.ListenUDP("udp4", listenAddr)
	if err != nil {
		fmt.Printf("ListenUDP Failed. %v\n", err)
		return
	}
	defer broadcastServer.Close()
	fmt.Printf("Server Started.\n")

	ctx := context.Background()
	go LANServer(ctx, broadcastServer)
	go LANClient(ctx, broadcastServer)
	select {
	case <-ctx.Done():
		fmt.Printf("ctx Done: %v", <-ctx.Done())
	}
}