Fix: fuck udp

utils/udp.go

@@ -3,6 +3,7 @@ package utils
 import (
 	"fmt"
 	"net"
+	"time"
 
 	"gitea.konchin.com/ytshih/inp2025/types"
 	"github.com/vmihailenco/msgpack/v5"
@@ -11,6 +12,8 @@ import (
 const (
 	BUFFER_SIZE  int = 1024
 	MAGIC_NUMBER int = 114514
+
+	LISTEN_TIMEOUT = 200 * time.Millisecond
 )
 
 type UDPReqType int
@@ -36,24 +39,36 @@ func ListenUDPData(
 	return ListenUDP(port, dataCh, nil)
 }
 
-func Ping(endpoint string) error {
+func Ping(endpoints []string) ([]string, error) {
 	pingCh := make(chan string)
 	local, shutdown, err := ListenUDP(0, nil, pingCh)
 	if err != nil {
-		return err
+		return []string{}, err
 	}
 	defer shutdown()
 
-	err = SendRawPayload(endpoint, UDPPayload{
-		MagicNumber: MAGIC_NUMBER,
-		Endpoint:    local,
-		Type:        UDPReqTypePingRequest,
-	})
-	if err != nil {
-		return err
+	for _, endpoint := range endpoints {
+		SendRawPayload(endpoint, UDPPayload{
+			MagicNumber: MAGIC_NUMBER,
+			Endpoint:    local,
+			Type:        UDPReqTypePingRequest,
+		})
+	}
+
+	doneCh := make(chan struct{})
+	go func() {
+		time.Sleep(LISTEN_TIMEOUT)
+		doneCh <- struct{}{}
+	}()
+	ret := []string{}
+	for {
+		select {
+		case <-doneCh:
+			return ret, nil
+		case endpoint := <-pingCh:
+			ret = append(ret, endpoint)
+		}
 	}
-	<-pingCh
-	return nil
 }
 
 func ListenUDP(