Add sip-to-webrtc

Example demonstrates how to connect to FreeSWITCH and save to disk

Co-authored-by: Sean DuBois <sean@siobud.com>

Author: Pascal Benoit

sip-to-webrtc/README.md

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+# sip-to-webrtc
+sip-to-webrtc demonstrates how you can connect to a SIP over WebRTC endpoint. This example connects to an extension
+and saves the audio to a ogg file.
+
+## Instructions
+### Setup FreeSWITCH (or SIP over WebSocket Server)
+With a fresh install of FreeSWITCH all you need to do is
+
+* Enable `ws-binding`
+* Set a `default_password` to something you know
+
+### Run `sip-to-webrtc`
+Run `go run *.go -h` to see the arguments of the program. If everything is working
+this is the output you will see.
+
+```
+$ go run *.go -host 172.17.0.2 -password Aelo1ievoh2oopooTh2paijaeNaidiek
+  Connection State has changed checking
+  Connection State has changed connected
+  Got Opus track, saving to disk as output.ogg
+  Connection State has changed disconnected
+```
+
+### Play the audio file
+ffmpeg's in-tree Opus decoder isn't able to play the default audio file from FreeSWITCH. Use the following command to force libopus.
+
+`ffplay -acodec libopus output.ogg`

sip-to-webrtc/main.go

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+package main
+
+import (
+	"flag"
+	"fmt"
+
+	"github.com/pion/example-webrtc-applications/sip-to-webrtc/softphone"
+	"github.com/pion/sdp/v2"
+	"github.com/pion/webrtc/v3"
+	"github.com/pion/webrtc/v3/pkg/media/oggwriter"
+)
+
+var (
+	username  = flag.String("username", "1000", "Extension you wish to register as")
+	password  = flag.String("password", "", "Password for the extension you wish to register as")
+	extension = flag.String("extension", "9198", "Extension you wish to call")
+	host      = flag.String("host", "", "Host that websocket is available on")
+	port      = flag.String("port", "5066", "Port that websocket is available on")
+)
+
+func main() {
+	flag.Parse()
+
+	if *host == "" || *port == "" || *password == "" {
+		panic("-host -port and -password are required")
+	}
+
+	conn := softphone.NewSoftPhone(softphone.SIPInfoResponse{
+		Username:        *username,
+		AuthorizationID: *username,
+		Password:        *password,
+		Domain:          *host,
+		Transport:       "ws",
+		OutboundProxy:   *host + ":" + *port,
+	})
+
+	pc, err := webrtc.NewPeerConnection(webrtc.Configuration{})
+	if err != nil {
+		panic(err)
+	}
+
+	pc.OnICEConnectionStateChange(func(connectionState webrtc.ICEConnectionState) {
+		fmt.Printf("Connection State has changed %s \n", connectionState.String())
+	})
+
+	oggFile, err := oggwriter.New("output.ogg", 48000, 2)
+	if err != nil {
+		panic(err)
+	}
+
+	pc.OnTrack(func(track *webrtc.TrackRemote, receiver *webrtc.RTPReceiver) {
+		fmt.Println("Got Opus track, saving to disk as output.ogg")
+
+		for {
+			rtpPacket, _, readErr := track.ReadRTP()
+			if readErr != nil {
+				panic(readErr)
+			}
+			if readErr := oggFile.WriteRTP(rtpPacket); readErr != nil {
+				panic(readErr)
+			}
+		}
+	})
+
+	if _, err = pc.AddTransceiverFromKind(webrtc.RTPCodecTypeAudio); err != nil {
+		panic(err)
+	}
+
+	offer, err := pc.CreateOffer(nil)
+	if err != nil {
+		panic(err)
+	}
+
+	if err := pc.SetLocalDescription(offer); err != nil {
+		panic(err)
+	}
+
+	gotAnswer := false
+
+	conn.OnOK(func(okBody string) {
+		if gotAnswer {
+			return
+		}
+		gotAnswer = true
+
+		okBody += "a=mid:0\r\n"
+		if err := pc.SetRemoteDescription(webrtc.SessionDescription{Type: webrtc.SDPTypeAnswer, SDP: okBody}); err != nil {
+			panic(err)
+		}
+	})
+	conn.Invite(*extension, rewriteSDP(offer.SDP))
+
+	select {}
+}
+
+// Apply the following transformations for FreeSWITCH
+// * Add fake srflx candidate to each media section
+// * Add msid to each media section
+// * Make bundle first attribute at session level.
+func rewriteSDP(in string) string {
+	parsed := &sdp.SessionDescription{}
+	if err := parsed.Unmarshal([]byte(in)); err != nil {
+		panic(err)
+	}
+
+	// Reverse global attributes
+	for i, j := 0, len(parsed.Attributes)-1; i < j; i, j = i+1, j-1 {
+		parsed.Attributes[i], parsed.Attributes[j] = parsed.Attributes[j], parsed.Attributes[i]
+	}
+
+	parsed.MediaDescriptions[0].Attributes = append(parsed.MediaDescriptions[0].Attributes, sdp.Attribute{
+		Key:   "candidate",
+		Value: "79019993 1 udp 1686052607 1.1.1.1 9 typ srflx",
+	})
+
+	out, err := parsed.Marshal()
+	if err != nil {
+		panic(err)
+	}
+
+	return string(out)
+}

sip-to-webrtc/output.ogg

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+package softphone
+
+var responseCodes = map[int]string{
+	100: "Trying",
+	180: "Ringing",
+	181: "Call is Being Forwarded",
+	182: "Queued",
+	183: "Session Progress",
+	199: "Early Dialog Terminated",
+	200: "OK",
+	202: "Accepted",
+	204: "No Notification",
+	300: "Multiple Choices",
+	301: "Moved Permanently",
+	302: "Moved Temporarily",
+	305: "Use Proxy",
+	380: "Alternative Service",
+	400: "Bad Request",
+	401: "Unauthorized",
+	402: "Payment Required",
+	403: "Forbidden",
+	404: "Not Found",
+	405: "Method Not Allowed",
+	406: "Not Acceptable",
+	407: "Proxy Authentication Required",
+	408: "Request Timeout",
+	409: "Conflict",
+	410: "Gone",
+	411: "Length Required",
+	412: "Conditional Request Failed",
+	413: "Request Entity Too Large",
+	414: "Request-URI Too Long",
+	415: "Unsupported Media Type",
+	416: "Unsupported URI Scheme",
+	417: "Unknown Resource-Priority",
+	420: "Bad Extension",
+	421: "Extension Required",
+	422: "Session Interval Too Small",
+	423: "Interval Too Brief",
+	424: "Bad Location Information",
+	428: "Use Identity Header",
+	429: "Provide Referrer Identity",
+	433: "Anonymity Disallowed",
+	436: "Bad Identity-Info",
+	437: "Unsupported Certificate",
+	438: "Invalid Identity Header",
+	439: "First Hop Lacks Outbound Support",
+	440: "Max-Breadth Exceeded",
+	469: "Bad Info Package",
+	470: "Consent Needed",
+	480: "Temporarily Unavailable",
+	481: "Call/Transaction Does Not Exist",
+	482: "Loop Detected",
+	483: "Too Many Hops",
+	484: "Address Incomplete",
+	485: "Ambiguous",
+	486: "Busy Here",
+	487: "Request Terminated",
+	488: "Not Acceptable Here",
+	489: "Bad Event",
+	491: "Request Pending",
+	493: "Undecipherable",
+	494: "Security Agreement Required",
+	500: "Server Internal Error",
+	501: "Not Implemented",
+	502: "Bad Gateway",
+	503: "Service Unavailable",
+	504: "Server Time-out",
+	505: "Version Not Supported",
+	513: "Message Too Large",
+	580: "Precondition Failure",
+	600: "Busy Everywhere",
+	603: "Decline",
+	604: "Does Not Exist Anywhere",
+	606: "Not Acceptable",
+	607: "Unwanted",
+}

sip-to-webrtc/softphone/constants.go

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+package softphone
+
+import (
+	"encoding/xml"
+	"fmt"
+	"log"
+	"strings"
+)
+
+// OpenToInvite adds a handler that responds to any incoming invites.
+func (softphone *Softphone) OpenToInvite() {
+	softphone.inviteKey = softphone.addMessageListener(func(message string) {
+		if strings.HasPrefix(message, "INVITE sip:") {
+			inviteMessage := SIPMessage{}.FromString(message)
+
+			dict := map[string]string{"Contact": fmt.Sprintf(`<sip:%s;transport=ws>`, softphone.fakeDomain)}
+			responseMsg := inviteMessage.Response(*softphone, 180, dict, "")
+			softphone.response(responseMsg)
+
+			var msg Msg
+			if err := xml.Unmarshal([]byte(inviteMessage.headers["P-rc"]), &msg); err != nil {
+				log.Panic(err)
+			}
+			sipMessage := SIPMessage{}
+			sipMessage.method = "MESSAGE"
+			sipMessage.address = msg.Hdr.From
+			sipMessage.headers = make(map[string]string)
+			sipMessage.headers["Via"] = fmt.Sprintf("SIP/2.0/WSS %s;branch=%s", softphone.fakeDomain, branch())
+			sipMessage.headers["From"] = fmt.Sprintf("<sip:%s@%s>;tag=%s", softphone.sipInfo.Username, softphone.sipInfo.Domain, softphone.fromTag)
+			sipMessage.headers["To"] = fmt.Sprintf("<sip:%s>", msg.Hdr.From)
+			sipMessage.headers["Content-Type"] = "x-rc/agent"
+			sipMessage.addCseq(softphone).addCallID(*softphone).addUserAgent()
+			sipMessage.Body = fmt.Sprintf(`<Msg><Hdr SID="%s" Req="%s" From="%s" To="%s" Cmd="17"/><Bdy Cln="%s"/></Msg>`, msg.Hdr.SID, msg.Hdr.Req, msg.Hdr.To, msg.Hdr.From, softphone.sipInfo.AuthorizationID)
+			softphone.request(sipMessage, nil)
+
+			softphone.OnInvite(inviteMessage)
+		}
+	})
+}
+
+// CloseToInvite removes the previously set invite listener.
+func (softphone *Softphone) CloseToInvite() {
+	softphone.removeMessageListener(softphone.inviteKey)
+}
+
+// OnOK adds a handler that responds to any incoming ok events.
+func (softphone *Softphone) OnOK(hdlr func(string)) {
+	softphone.addMessageListener(func(message string) {
+		if strings.HasPrefix(message, "SIP/2.0 200 OK") {
+			parsed := SIPMessage{}.FromString(message)
+			hdlr(parsed.Body)
+		}
+	})
+}

sip-to-webrtc/softphone/inboundcall.go

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+package softphone
+
+import (
+	"fmt"
+	"regexp"
+)
+
+// Invite ...
+func (softphone *Softphone) Invite(extension, offer string) {
+	sipMessage := SIPMessage{headers: map[string]string{}}
+
+	sipMessage.method = "INVITE"
+	sipMessage.address = softphone.sipInfo.Domain
+
+	sipMessage.headers["Contact"] = fmt.Sprintf("<sip:%s;transport=ws>;expires=200", softphone.FakeEmail)
+	sipMessage.headers["To"] = fmt.Sprintf("<sip:%s@%s>", extension, softphone.sipInfo.Domain)
+	sipMessage.headers["Via"] = fmt.Sprintf("SIP/2.0/WS %s;branch=%s", softphone.fakeDomain, branch())
+	sipMessage.headers["From"] = fmt.Sprintf("<sip:%s@%s>;tag=%s", softphone.sipInfo.Username, softphone.sipInfo.Domain, softphone.fromTag)
+	sipMessage.headers["Supported"] = "replaces, outbound,ice"
+	sipMessage.addCseq(softphone).addCallID(*softphone).addUserAgent()
+
+	sipMessage.headers["Content-Type"] = "application/sdp"
+	sipMessage.Body = offer
+
+	softphone.request(sipMessage, func(message string) bool {
+		authenticateHeader := SIPMessage{}.FromString(message).headers["Proxy-Authenticate"]
+		regex := regexp.MustCompile(`, nonce="(.+?)"`)
+		nonce := regex.FindStringSubmatch(authenticateHeader)[1]
+
+		sipMessage.addProxyAuthorization(*softphone, nonce, extension, "INVITE").addCseq(softphone).newViaBranch()
+		softphone.request(sipMessage, func(msg string) bool {
+			return false
+		})
+
+		return true
+	})
+}

sip-to-webrtc/softphone/invite.go

@@ -0,0 +1,32 @@
+package softphone
+
+import "encoding/xml"
+
+// Msg ...
+type Msg struct {
+	XMLName xml.Name `xml:"Msg"`
+	Hdr     Hdr      `xml:"Hdr"`
+	Bdy     Bdy      `xml:"Bdy"`
+}
+
+// Hdr ...
+type Hdr struct {
+	XMLName xml.Name `xml:"Hdr"`
+	SID     string   `xml:"SID,attr"`
+	Req     string   `xml:"Req,attr"`
+	From    string   `xml:"From,attr"`
+	To      string   `xml:"To,attr"`
+	Cmd     string   `xml:"Cmd,attr"`
+}
+
+// Bdy ...
+type Bdy struct {
+	XMLName   xml.Name `xml:"Bdy"`
+	SrvLvl    string   `xml:"SrvLvl,attr"`
+	SrvLvlExt string   `xml:"SrvLvlExt,attr"`
+	Phn       string   `xml:"Phn,attr"`
+	Nm        string   `xml:"Nm,attr"`
+	ToPhn     string   `xml:"ToPhn,attr"`
+	ToNm      string   `xml:"ToNm,attr"`
+	RecURL    string   `xml:"RecUrl,attr"`
+}