diff --git a/.gitea/workflows/build.yml b/.gitea/workflows/build.yml
new file mode 100644
index 0000000..b277cfb
--- /dev/null
+++ b/.gitea/workflows/build.yml
@@ -0,0 +1,53 @@
+---
+name: catsync-build
+on:
+  push:
+    paths:
+      - '.gitea/workflows/build.yml'
+      - 'go.mod'
+      - 'go.sum'
+      - 'main.go'
+      - 'assets/**'
+      - 'pb/**'
+  pull_request:
+    paths:
+      - '.gitea/workflows/build.yml'
+      - 'go.mod'
+      - 'go.sum'
+      - 'main.go'
+      - 'assets/**'
+      - 'pb/**'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    name: simple-build
+    runs-on: ubuntu-20.04
+    strategy:
+      matrix:
+        goos: [linux, windows]
+        goarch: [amd64, arm64]
+        gover: ['1.23.1', 'oldstable']
+        exclude:
+          - goarch: arm64
+            goos: windows
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v3
+        with:
+          go-version: ${{ matrix.gover }}
+      - name: install-tools
+        run: |
+          apt-get update -y 
+          apt-get install -y protobuf-compiler
+          go install google.golang.org/protobuf/cmd/protoc-gen-go@v1.36.0
+      - name: protobuf-gen
+        run: |
+          protoc --go_out=. ./assets/protobuf/*.proto
+      - name: build
+        run: |
+          GOOS=${{ matrix.goos }} GOARCH=${{ matrix.goarch }} go build -x .
+
diff --git a/.gitignore b/.gitignore
index 1b1402c..0be7c57 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,7 +1,2 @@
-out/
-build/
-cmake-kits.json
-.cache/
-.idea
-compile_commands.json
-*.a
+catsync
+pb/
diff --git a/CHANGELOG.md b/CHANGELOG.md
deleted file mode 100644
index e69de29..0000000
diff --git a/assets/protobuf/peer_message.proto b/assets/protobuf/peer_message.proto
new file mode 100644
index 0000000..7dc567c
--- /dev/null
+++ b/assets/protobuf/peer_message.proto
@@ -0,0 +1,20 @@
+syntax="proto3";
+package main;
+option go_package = "/pb";
+
+import public "google/protobuf/timestamp.proto";
+
+message PeerMessage {
+    uint32 magic_number= 1;
+    uint32 version = 2;
+    PeerMessageType type = 3;
+    google.protobuf.Timestamp send_timestamp = 4;
+
+    string uid = 5;
+}
+
+enum PeerMessageType {
+    PEER_MESSAGE_TYPE_REQUEST = 0;
+    PEER_MESSAGE_TYPE_RESPONSE = 1;
+    PEER_MESSAGE_TYPE_ACK = 2;
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..3efdae4
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,7 @@
+module code.uocat.com/tqcq/catsync
+
+go 1.23.3
+
+require (
+	google.golang.org/protobuf v1.36.0 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..d093a77
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+google.golang.org/protobuf v1.36.0 h1:mjIs9gYtt56AzC4ZaffQuh88TZurBGhIJMBZGSxNerQ=
+google.golang.org/protobuf v1.36.0/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..a85f627
--- /dev/null
+++ b/main.go
@@ -0,0 +1,96 @@
+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())
+	}
+}