added payload-protocol-identifier code.

lib/association.js

@@ -1781,7 +1781,7 @@ class Association extends EventEmitter {
           },
           stream_id: streamId,
           ssn: this.ssn[streamId],
-          ppid: options.streamId,
+          ppid: options.ppid,
           user_data: buffer.slice(offset, offset + mtu)
         }
         offset += mtu
@@ -1797,7 +1797,7 @@ class Association extends EventEmitter {
         },
         stream_id: streamId,
         ssn: this.ssn[streamId],
-        ppid: options.streamId,
+        ppid: options.ppid,
         user_data: buffer
       }
       this._sendChunk('data', chunk, null, callback)

lib/sockets.js

@@ -12,6 +12,7 @@ const EventEmitter = require('events').EventEmitter
 const debug = require('debug')
 const ip = require('ip')
 const Endpoint = require('./endpoint')
+const defs = require('./defs')
 
 class SCTPStreamReadable extends Readable {
   // Constructor is useless
@@ -41,9 +42,32 @@ class SCTPStreamWritable extends Writable {
     if (!this.socket.association) {
       return callback(new Error('no association established'))
     }
-    const options = {}
-    options.stream_id = this.stream_id
-    this.bytesWritten += chunk.length
+    // Set ppid (payload-protocol-identifier)
+    // more info:
+    // https://webrtcforthecurious.com/docs/07-data-communication/#payload-protocol-identifier 
+    let ppid
+
+    // Data is binary?
+    if (chunk.length == 0) {
+      // if No data, lenght == 0, then 
+      // chunk = add ceros 'like firefox'
+      // and set ppid to empty code with flavor Binary or String.
+      chunk = Buffer.from('00000000', 'hex')
+      ppid = encoding === 'buffer' 
+        ? defs.PPID.WEBRTC_BINARY_EMPTY
+        : defs.PPID.WEBRTC_STRING_EMPTY
+    } else {
+      // set ppid to data code with flavor Binary or String.
+      ppid = encoding === 'buffer' 
+        ? defs.PPID.WEBRTC_BINARY
+        : defs.PPID.WEBRTC_STRING
+    }
+
+    const options = {
+      stream_id: this.stream_id,
+      unordered: this.socket.unordered,
+      ppid,
+    }
     this.socket.bytesWritten += chunk.length
     return this.socket.association.SEND(chunk, options, callback)
   }