package localchat import ( "encoding/json" "fmt" "log" "net" "net/http" "golang.org/x/net/ipv4" ) type UdpMessage struct { Type string `json:"type"` IP string `json:"ip"` Hostname string `json:"hostname"` Message any `json:"message"` } // 多播地址列表 var multicastAddrs = []string{"239.255.255.250:2024", "239.255.255.251:2024", "224.0.0.251:1234", "224.0.0.1:1679"} var OnlineUsers = make(map[string]UdpMessage) // 全局map,key为IP,value为主机名 // SendMulticast 发送多播消息 func init() { go InitMulticast() go ListenForMulticast() } func InitMulticast() { myIP, myHostname, err := GetMyIPAndHostname() if err != nil { return } message := UdpMessage{ Type: "online", IP: myIP, Hostname: myHostname, Message: "online", } SendMulticast(message) } func SendMulticast(message UdpMessage) error { for _, addrStr := range multicastAddrs { addr, err := net.ResolveUDPAddr("udp4", addrStr) if err != nil { return err } conn, err := net.DialUDP("udp4", nil, addr) if err != nil { return err } defer conn.Close() data, err := json.Marshal(message) if err != nil { return err } _, err = conn.WriteToUDP(data, addr) if err != nil { return err } fmt.Printf("发送多播消息到 %s 成功\n", addrStr) } return nil } // ListenForMulticast 监听多播消息 func ListenForMulticast() { // 选择一个可用的多播地址 var multicastGroup *net.UDPAddr var err error for _, addrStr := range multicastAddrs { multicastGroup, err = net.ResolveUDPAddr("udp4", addrStr) if err != nil { fmt.Println("Error resolving UDP address:", err) continue } break } if multicastGroup == nil { fmt.Println("No available multicast address found") return } conn, err := net.ListenUDP("udp4", &net.UDPAddr{IP: net.IPv4zero, Port: 2024}) if err != nil { fmt.Println("Error listening on UDP address:", err) return } defer conn.Close() udpConn := ipv4.NewPacketConn(conn) // 获取本地网络接口 localIfaces, err := net.Interfaces() if err != nil { log.Fatalf("Failed to get local interfaces: %v", err) } // 选择一个可用的网络接口 var localInterface *net.Interface for _, iface := range localIfaces { addrs, err := iface.Addrs() if err != nil { continue } for _, addr := range addrs { if ipNet, ok := addr.(*net.IPNet); ok && !ipNet.IP.IsLoopback() { if ipNet.IP.To4() != nil { localInterface = &iface break } } } if localInterface != nil { break } } if localInterface == nil { log.Fatal("No suitable network interface found") } if err := udpConn.JoinGroup(localInterface, multicastGroup); err != nil { log.Fatalf("Failed to join multicast group: %v", err) } buffer := make([]byte, 1024) for { n, _, src, err := udpConn.ReadFrom(buffer) if err != nil { log.Printf("Error reading from UDP: %v, addr: %v", err, src) continue } var udpMsg UdpMessage err = json.Unmarshal(buffer[:n], &udpMsg) if err != nil { fmt.Printf("Error unmarshalling JSON: %v\n", err) continue } OnlineUsers[udpMsg.IP] = udpMsg if udpMsg.Type == "file" { RecieveFile(udpMsg) } fmt.Printf("Received message from %s: %s\n", udpMsg.IP, udpMsg.Hostname) } } // SendToIP 向指定的 IP 地址发送 UDP 消息 func SendToIP(ip string, message UdpMessage) error { addr, err := net.ResolveUDPAddr("udp4", fmt.Sprintf("%s:2024", ip)) if err != nil { return err } conn, err := net.DialUDP("udp4", nil, addr) if err != nil { return err } defer conn.Close() data, err := json.Marshal(message) if err != nil { return err } _, err = conn.WriteToUDP(data, addr) if err != nil { return err } fmt.Printf("发送 UDP 消息到 %s 成功\n", ip) return nil } // 获取 OnlineUsers 的最新状态 func GetOnlineUsers() map[string]UdpMessage { return OnlineUsers } func HandleMessage(w http.ResponseWriter, r *http.Request) { var msg UdpMessage decoder := json.NewDecoder(r.Body) if err := decoder.Decode(&msg); err != nil { http.Error(w, "Invalid request body", http.StatusBadRequest) return } defer r.Body.Close() ip := msg.IP preferredIP, err := GetMyIp() if err != nil { http.Error(w, "Failed to get preferred IP", http.StatusInternalServerError) return } msg.IP = preferredIP err = SendToIP(ip, msg) if err != nil { http.Error(w, "Failed to send message", http.StatusInternalServerError) return } w.WriteHeader(http.StatusOK) fmt.Fprintln(w, "Text message send successfully") }