partly works

src/croc/croc.go

@@ -304,6 +304,16 @@ func (c *Client) Send(options TransferOptions) (err error) {
 		log.Debugf("connection established: %+v", conn)
 		for {
 			data, _ := conn.Receive()
+			if bytes.Equal(data, []byte("ips?")) {
+				var ips []string
+				ips, err = utils.GetLocalIPs()
+				if err != nil {
+					log.Debugf("error getting local ips: %s", err.Error())
+				}
+				ips = append([]string{c.Options.RelayPorts[0]}, ips...)
+				bips, _ := json.Marshal(ips)
+				conn.Send(bips)
+			}
 			if bytes.Equal(data, []byte("handshake")) {
 				break
 			}
@@ -324,6 +334,7 @@ func (c *Client) Receive() (err error) {
 	fmt.Fprintf(os.Stderr, "connecting...")
 	// recipient will look for peers first
 	// and continue if it doesn't find any within 100 ms
+	usingLocal := false
 	if !c.Options.DisableLocal {
 		log.Debug("attempt to discover peers")
 		discoveries, err := peerdiscovery.Discover(peerdiscovery.Settings{
@@ -336,6 +347,7 @@ func (c *Client) Receive() (err error) {
 			log.Debug("switching to local")
 			c.Options.RelayAddress = fmt.Sprintf("%s:%s", discoveries[0].Address, discoveries[0].Payload)
 			c.ExternalIPConnected = c.Options.RelayAddress
+			usingLocal = true
 		}
 		log.Debugf("discoveries: %+v", discoveries)
 		log.Debug("establishing connection")
@@ -348,6 +360,18 @@ func (c *Client) Receive() (err error) {
 		return
 	}
 	log.Debugf("connection established: %+v", c.conn[0])
+
+	if !usingLocal && !c.Options.DisableLocal {
+		// ask the sender for their local ips and port
+		// and try to connect to them
+		var data []byte
+		c.conn[0].Send([]byte("ips?"))
+		data, err = c.conn[0].Receive()
+		if err != nil {
+			return
+		}
+		log.Debugf("ips data: %s", data)
+	}
 	c.conn[0].Send([]byte("handshake"))
 	c.Options.RelayPorts = strings.Split(banner, ",")
 	log.Debug("exchanged header message")

src/croc/croc_test.go

@@ -27,6 +27,7 @@ func TestCroc(t *testing.T) {
 		SharedSecret: "test",
 		Debug:        true,
 		RelayAddress: "localhost:8081",
+		RelayPorts:   []string{"8081"},
 		Stdout:       false,
 		NoPrompt:     true,
 		DisableLocal: true,

src/utils/utils.go

@@ -209,3 +209,20 @@ func ChunkRangesToChunks(chunkRanges []int64) (chunks []int64) {
 	}
 	return
 }
+
+func GetLocalIPs() (ips []string, err error) {
+	addrs, err := net.InterfaceAddrs()
+	if err != nil {
+		return
+	}
+	ips = []string{}
+	for _, address := range addrs {
+		// check the address type and if it is not a loopback the display it
+		if ipnet, ok := address.(*net.IPNet); ok && !ipnet.IP.IsLoopback() {
+			if ipnet.IP.To4() != nil {
+				ips = append(ips, ipnet.IP.String())
+			}
+		}
+	}
+	return
+}

src/utils/utils_test.go

@@ -35,6 +35,7 @@ func BenchmarkImoHash(b *testing.B) {
 }
 
 func TestExists(t *testing.T) {
+	fmt.Println(GetLocalIPs())
 	assert.True(t, Exists("bigfile.test"))
 	assert.False(t, Exists("doesnotexist"))
 }