Add new sessionTransportDisconnected event to TransportTCP

Helps us detect errors on socket ends and notify them to SIP.js clients properly

Also remade callIndex assembly to ease parsing and improved logging

src/TransportTCP.js

@@ -71,11 +71,12 @@ Transport.prototype = {
         callTag = parsedMsg.from_tag;
       }
       if (callId && callTag) {
-        let socket = this.sockets[callId + callTag];
+        const callIndex = `${callId}|${callTag}`;
+        let socket = this.sockets[callIndex]
         if (socket) {
           socket.write(message, (e) => {
             if (e) {
-              this.logger.warn('unable to send TCP message with error', e);
+              this.logger.warn(`unable to send TCP message with error ${e}`);
               return false;
             }
             if (this.ua.configuration.traceSip === true) {
@@ -169,14 +170,16 @@ Transport.prototype = {
     this.server = net.createServer((socket) => {
       socket.pendingSegments = [];
       socket.setKeepAlive(true);
-      socket.on('end', function() {
-        transport.onClose(socket);
+      socket.on('end', (e) => {
+        this.logger.log(`TCP socket ended for connection ${socket.callIndex || 'Unknown'}`);
+        transport.onClientSocketClose(socket, e);
       });
 
       const onSocketError = (e) => {
         this.logger.log("TCP socket returned error " + e + " and will close");
         if (socket.callIndex) {
-          //this.logger.log("TCP socket ended for connection" + socket.callIndex);
+          this.logger.log(`TCP socket ended for connection ${socket.callIndex}`);
+          transport.onClientSocketClose(socket, e);
           if (this.sockets[socket.callIndex]) {
             delete this.sockets[socket.callIndex];
           }
@@ -236,13 +239,29 @@ Transport.prototype = {
   */
   onClose: function(socket) {
     this.stopSendingKeepAlives();
+    this.ua.onTransportClosed(this);
     this.ua.emit('disconnected', {
       transport: this,
       code: "",
       reason: ""
     });
   },
 
+  /**
+  * @event
+  * @param {net.Socket} socket
+  * @param {event} e
+  */
+  onClientSocketClose: function(socket, e = {}) {
+    const callId = socket.callIndex? socket.callIndex.split('|')[0] : ''
+    this.ua.emit('sessionTransportDisconnected', {
+      transport: this,
+      callId,
+      code: e.code || '',
+      reason: e.message || ''
+    });
+  },
+
   /**
   * @event
   * @param {event} e
@@ -333,8 +352,9 @@ Transport.prototype = {
           switch (message.method) {
             case SIP.C.INVITE:
               if (this.sockets[message.call_id + message.from_tag] == null) {
-                socket.callIndex = message.call_id + message.from_tag;
-                this.sockets[message.call_id + message.from_tag] = socket;
+                const callIndex = `${message.call_id}|${message.from_tag}`;
+                socket.callIndex = callIndex;
+                this.sockets[callIndex] = socket;
               }
               break;
             default: