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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")
}