110 lines
2.2 KiB
Go
110 lines
2.2 KiB
Go
package main
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import (
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"encoding/base64"
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"encoding/binary"
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"errors"
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"fmt"
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"net"
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"strings"
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"time"
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"github.com/google/gopacket"
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"github.com/google/gopacket/pcap"
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)
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func errCheck(err error) {
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if err != nil {
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panic(err)
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}
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return
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}
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func listenDiscoverResponse(addrChan chan string, readyFlag chan int) {
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handle, err := pcap.OpenLive("any", int32(1600), true, pcap.BlockForever)
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errCheck(err)
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err = handle.SetBPFFilter("udp and port 8850")
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errCheck(err)
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packets := gopacket.NewPacketSource(handle, handle.LinkType()).Packets()
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readyFlag <- 1
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for pkt := range packets {
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msg, err := base64.StdEncoding.DecodeString(string(pkt.ApplicationLayer().Payload()))
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if err == nil {
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if strings.Contains(string(msg), "clientapi") {
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addrChan <- string(msg)
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return
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}
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}
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}
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return
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}
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func toMaxHost(n *net.IPNet) (net.IP, error) {
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if n.IP.To4() == nil {
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return net.IP{}, errors.New("IP address is not IPv4")
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}
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ip := make(net.IP, len(n.IP.To4()))
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binary.BigEndian.PutUint32(ip,
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binary.BigEndian.Uint32(n.IP.To4())|^binary.BigEndian.Uint32(net.IP(n.Mask).To4()))
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return ip, nil
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}
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func bcastAddresses() []string {
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var addrs []string = nil
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interfaceInfo, _ := net.Interfaces()
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for i := 0; i < len(interfaceInfo); i++ {
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addr, err := interfaceInfo[i].Addrs()
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errCheck(err)
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for j := 0; j < len(addr); j++ {
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_, ipNet, _ := net.ParseCIDR(addr[j].String())
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bcast, err := toMaxHost(ipNet)
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if err != nil {
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} else {
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addrs = append(addrs, bcast.String())
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}
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}
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}
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return addrs
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}
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func main() {
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sendAddrs := bcastAddresses()
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addrChan := make(chan string)
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readyFlag := make(chan int)
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go listenDiscoverResponse(addrChan, readyFlag)
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// Wait for device to listen
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<- readyFlag
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for i := 0; i < len(sendAddrs); i++ {
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remoteAddr := sendAddrs[i] + ":8888"
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remote, err := net.ResolveUDPAddr("udp4", remoteAddr)
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errCheck(err)
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conn, err := net.DialUDP("udp4", nil, remote)
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errCheck(err)
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defer conn.Close()
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_, err = conn.Write([]byte(conn.LocalAddr().String() + "here"))
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errCheck(err)
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}
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// Listen timeout
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select {
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case returnMSG := <- addrChan:
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fmt.Printf("%s\n", strings.Fields(returnMSG)[1])
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case <- time.After(5 * time.Second):
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fmt.Printf("error\n")
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}
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}
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