requirebin sketch

index.js

var servers = {username: "1427391317", credential: "yaRtZa0/GJOmOHy4ONLI3kHCJ6E=", url: "turn:104.130.195.95"};
var pc = new webkitRTCPeerConnection({
  iceServers: [servers],
  iceTransports: 'relay'
});
pc.oniceconnectionstatechange = function () { console.log('state', pc.iceConnectionState); };
var pc2 = new webkitRTCPeerConnection({
  iceServers: [servers],
  iceTransports: 'relay'
});
var recvChannel;
pc2.ondatachannel = function (event) {
  recvChannel = event.channel;
  recvChannel.onmessage = function (event) { console.log('recv', event.data); };
};
pc2.onicecandidate = function (event) {
  if (!event.candidate) {
    min = reduce(pc2.localDescription);
    console.log('answer', min.length, min);
    pc.setRemoteDescription(new RTCSessionDescription(expand(min)));
  }
};
var sendChannel = pc.createDataChannel("signaling", {protocol: "madtweetsdpprotocol"});
pc.createOffer(function (offer) {
  pc.setLocalDescription(offer);
});
pc.onicecandidate = function (event) {
  if (!event.candidate) {
    min = reduce(pc.localDescription);
    console.log('offer', min.length, min);
    pc2.setRemoteDescription(new RTCSessionDescription(expand(min)),
      function () {
        pc2.createAnswer(function (answer) {
          pc2.setLocalDescription(answer);
        }, function (err) {
          console.log('nay2', err);
        });
      },
      function (err) { console.log('nay', err); }
    );
  }
};

function reduce(desc) {
  var sdp = desc.sdp;
  var lines = sdp.split('\r\n');
  lines = lines.filter(function (line) {
    return line.indexOf('a=candidate:') === 0 ||
      line.indexOf('a=ice-ufrag:') === 0 ||
      line.indexOf('a=ice-pwd:') === 0 ||
      line.indexOf('a=fingerprint:') === 0;
  });
  lines = lines.sort().reverse().slice(0, 4); // chop off extra cands
  var comp = lines.map(function (line) {
    switch(line.split(':')[0]) {
      case 'a=fingerprint':
        var hex = line.substr(22).split(':').map(function (h) {
          return parseInt(h, 16);
        });
        // b64 is slightly more concise than colon-hex
        return btoa(String.fromCharCode.apply(String, hex));
      case 'a=ice-pwd':
        return line.substr(10); // already b64
      case 'a=ice-ufrag':
        return line.substr(12); // already b64
      case 'a=candidate':
        var parts = line.substr(12).split(' ');        
        var ip = parts[4].split('.').reduce(function (prev, cur) { return (prev << 8) + parseInt(cur, 10); });
        // take foundation, priority + ip/port from candidate, encode
        // not sure if foundation is required
        // can I have sprintf("%4c%4c%4c%2c" please? pike rocks
        return [parseInt(parts[0], 10), parseInt(parts[3], 10), ip, parseInt(parts[5])].map(function (a) { return a.toString(32); }).join(',');
    }
  });
  return [desc.type === 'offer' ? 'O' : 'A'].concat(comp).join(',');
}

function expand(str) {
  var comp = str.split(',');
  var sdp = ['v=0',
    'o=- 5498186869896684180 2 IN IP4 127.0.0.1',
    's=-', 't=0 0', 'a=msid-semantic: WMS',
    'm=application 9 DTLS/SCTP 5000',
    'c=IN IP4 0.0.0.0',
    'a=mid:data',
    'a=sctpmap:5000 webrtc-datachannel 1024'
  ];
  if (comp[0] === 'A') {
    sdp.push('a=setup:active');
  } else {
    sdp.push('a=setup:actpass');
  }
  sdp.push('a=ice-ufrag:' + comp[1]);
  sdp.push('a=ice-pwd:' + comp[2]);
  sdp.push('a=fingerprint:sha-256 ' + atob(comp[3]).split('').map(function (c) { var d = c.charCodeAt(0); var e = c.charCodeAt(0).toString(16).toUpperCase(); if (d < 16) e = '0' + e; return e; }).join(':'));
  var candparts = comp.splice(4).map(function (c) { return parseInt(c, 32); });
  var ip = [(candparts[2] >> 24) & 0xff, (candparts[2] >> 16) & 0xff, (candparts[2] >> 8) & 0xff, candparts[2] & 0xff].join('.');
  var cand = ['a=candidate:' + candparts[0],
     '1', 'udp',
     candparts[1],
     ip,
     candparts[3],
     'typ host' // well, not a host cand but...
  ];
  sdp.push(cand.join(' '));
  // depending on O/A role we need to append a=setup:actpass or a=setup:active
  return {type: comp[0] === 'O' ? 'offer' : 'answer', sdp:sdp.join('\r\n') + '\r\n'};
}

minified.js

var servers={username:"1427391317",credential:"yaRtZa0/GJOmOHy4ONLI3kHCJ6E=",url:"turn:104.130.195.95"};var pc=new webkitRTCPeerConnection({iceServers:[servers],iceTransports:"relay"});pc.oniceconnectionstatechange=function(){console.log("state",pc.iceConnectionState)};var pc2=new webkitRTCPeerConnection({iceServers:[servers],iceTransports:"relay"});var recvChannel;pc2.ondatachannel=function(event){recvChannel=event.channel;recvChannel.onmessage=function(event){console.log("recv",event.data)}};pc2.onicecandidate=function(event){if(!event.candidate){min=reduce(pc2.localDescription);console.log("answer",min.length,min);pc.setRemoteDescription(new RTCSessionDescription(expand(min)))}};var sendChannel=pc.createDataChannel("signaling",{protocol:"madtweetsdpprotocol"});pc.createOffer(function(offer){pc.setLocalDescription(offer)});pc.onicecandidate=function(event){if(!event.candidate){min=reduce(pc.localDescription);console.log("offer",min.length,min);pc2.setRemoteDescription(new RTCSessionDescription(expand(min)),function(){pc2.createAnswer(function(answer){pc2.setLocalDescription(answer)},function(err){console.log("nay2",err)})},function(err){console.log("nay",err)})}};function reduce(desc){var sdp=desc.sdp;var lines=sdp.split("\r\n");lines=lines.filter(function(line){return line.indexOf("a=candidate:")===0||line.indexOf("a=ice-ufrag:")===0||line.indexOf("a=ice-pwd:")===0||line.indexOf("a=fingerprint:")===0});lines=lines.sort().reverse().slice(0,4);var comp=lines.map(function(line){switch(line.split(":")[0]){case"a=fingerprint":var hex=line.substr(22).split(":").map(function(h){return parseInt(h,16)});return btoa(String.fromCharCode.apply(String,hex));case"a=ice-pwd":return line.substr(10);case"a=ice-ufrag":return line.substr(12);case"a=candidate":var parts=line.substr(12).split(" ");var ip=parts[4].split(".").reduce(function(prev,cur){return(prev<<8)+parseInt(cur,10)});return[parseInt(parts[0],10),parseInt(parts[3],10),ip,parseInt(parts[5])].map(function(a){return a.toString(32)}).join(",")}});return[desc.type==="offer"?"O":"A"].concat(comp).join(",")}function expand(str){var comp=str.split(",");var sdp=["v=0","o=- 5498186869896684180 2 IN IP4 127.0.0.1","s=-","t=0 0","a=msid-semantic: WMS","m=application 9 DTLS/SCTP 5000","c=IN IP4 0.0.0.0","a=mid:data","a=sctpmap:5000 webrtc-datachannel 1024"];if(comp[0]==="A"){sdp.push("a=setup:active")}else{sdp.push("a=setup:actpass")}sdp.push("a=ice-ufrag:"+comp[1]);sdp.push("a=ice-pwd:"+comp[2]);sdp.push("a=fingerprint:sha-256 "+atob(comp[3]).split("").map(function(c){var d=c.charCodeAt(0);var e=c.charCodeAt(0).toString(16).toUpperCase();if(d<16)e="0"+e;return e}).join(":"));var candparts=comp.splice(4).map(function(c){return parseInt(c,32)});var ip=[candparts[2]>>24&255,candparts[2]>>16&255,candparts[2]>>8&255,candparts[2]&255].join(".");var cand=["a=candidate:"+candparts[0],"1","udp",candparts[1],ip,candparts[3],"typ host"];sdp.push(cand.join(" "));return{type:comp[0]==="O"?"offer":"answer",sdp:sdp.join("\r\n")+"\r\n"}}

package.json

{
  "name": "requirebin-sketch",
  "version": "1.0.0"
}

page-head.html

<style type='text/css'>html, body { margin: 0; padding: 0; border: 0; }
body, html { height: 100%; width: 100%; }</style>

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