updated client

client/client.go

@@ -1,10 +1,12 @@
 package main
 
 import (
+	"encoding/base64"
 	"encoding/binary"
 	"errors"
 	"fmt"
 	"net"
+	"strings"
 	"time"
 
 	"github.com/google/gopacket"
@@ -18,16 +20,25 @@ func errCheck(err error) {
 	return
 }
 
-func listenDiscoverResponse() {
+func listenDiscoverResponse(addrChan chan string, readyFlag chan int) {
 	handle, err := pcap.OpenLive("any", int32(1600), true, pcap.BlockForever)
 	errCheck(err)
 
-	handle.SetBPFFilter("udp and port 8850")
+	err = handle.SetBPFFilter("udp and port 8850")
+	errCheck(err)
 
 	packets := gopacket.NewPacketSource(handle, handle.LinkType()).Packets()
 
+	readyFlag <- 1
+
 	for pkt := range packets {
-		fmt.Printf("%s\n", pkt.NetworkLayer().NetworkFlow().Src())
+		msg, err := base64.StdEncoding.DecodeString(string(pkt.ApplicationLayer().Payload()))
+		if err == nil {
+			if strings.Contains(string(msg), "clientapi") {
+				addrChan <- string(msg)
+				return
+			}
+		}
 	}
 
 	return
@@ -45,7 +56,7 @@ func toMaxHost(n *net.IPNet) (net.IP, error) {
 	return ip, nil
 }
 
-func bcastAddresses() ([]string) {
+func bcastAddresses() []string {
 	var addrs []string = nil
 	interfaceInfo, _ := net.Interfaces()
 	for i := 0; i < len(interfaceInfo); i++ {
@@ -68,9 +79,13 @@ func bcastAddresses() ([]string) {
 func main() {
 	sendAddrs := bcastAddresses()
 
-	go listenDiscoverResponse()
+	addrChan := make(chan string)
+	readyFlag := make(chan int)
 
-	time.Sleep(1 * time.Second)
+	go listenDiscoverResponse(addrChan, readyFlag)
+
+	// Wait for device to listen
+	<- readyFlag
 
 	for i := 0; i < len(sendAddrs); i++ {
 		remoteAddr := sendAddrs[i] + ":8888"
@@ -80,9 +95,15 @@ func main() {
 		errCheck(err)
 		defer conn.Close()
 
-		_, err = conn.Write([]byte(conn.LocalAddr().String()))
+		_, err = conn.Write([]byte(conn.LocalAddr().String() + "here"))
 		errCheck(err)
 	}
-	time.Sleep(30 * time.Second)
-}
 
+	// Listen timeout
+	select {
+		case returnMSG := <- addrChan:
+			fmt.Printf("Discovery Server: %s\n", strings.Fields(returnMSG)[1])
+		case <- time.After(5 * time.Second):
+			fmt.Printf("Discovery Server not found\n")
+	}
+}