UDP bugfix (#181)

- clamp UDPROS msgID to uint8
- host sent to the publisher during udp handshake was wrong

Author: Francesco Di Franco

src/lib/RosNode.js

@@ -596,17 +596,17 @@ class RosNode extends EventEmitter {
           let dgramSize = params[2][0][4];
           let resp = [
             1,
-            '',
+            ' ', // this string must not be empty, otherwise the subscriber will not understand the response
             [
               'UDPROS',
-              NetworkUtils.getHost(), //maybe wrong
-              port,
+              NetworkUtils.getHost(),
+              this._udprosPort,
               ++this._connections, //connection Id
               dgramSize,
               UdprosUtils.createPubHeader(this.getNodeName(), typeClass.md5sum(), typeClass.messageDefinition(), topic, header.type)
             ]
           ]
-          pub.addUdpSubscriber(resp[2])
+          pub.addUdpSubscriber(resp[2],host,port)
           callback(null, resp)
         }
       }

src/lib/impl/PublisherImpl.js

@@ -241,7 +241,7 @@ class PublisherImpl extends EventEmitter {
         if (this.getLatching()) {
           this._lastSentMsg = serializedMsg;
         }
-        msgCount++;
+        msgCount = msgCount > 254 ? 0 : ++msgCount;
       });
     }
     catch (err) {
@@ -362,13 +362,13 @@ class PublisherImpl extends EventEmitter {
     this.emit('connection', header, socket.name);
   }
 
-  addUdpSubscriber(resp){
+  addUdpSubscriber(resp,host,port){
     if(Object.keys(this._udpSubClients).length === 0){
       this.udpSocket = Udp.createSocket('udp4');
     }
     this._udpSubClients[resp[3]] = {
-      port: resp[2],
-      host: resp[1],
+      port: port,
+      host: host,
       dgramSize: resp[4],
       connId: resp[3]
     }

src/lib/impl/SubscriberImpl.js

@@ -282,7 +282,7 @@ class SubscriberImpl extends EventEmitter {
     }
     if(this._udp){
       let header = UdprosUtils.createSubHeader(this._nodeHandle.getNodeName(), this._messageHandler.md5sum(), this.getTopic(), this.getType())
-      protocols.push(['UDPROS', header, info.host, this._port, this._dgramSize || 1500])
+      protocols.push(['UDPROS', header, NetworkUtils.getHost(), this._port, this._dgramSize || 1500])
     }
     if(this._udpFirst){
       protocols.reverse();

src/utils/udpros_utils.js

@@ -81,16 +81,18 @@ let UdprosUtils = {
    * Creates a UDPROS connection header for a publisher to send.
    * @param callerId {string} node publishing this topic
    * @param md5sum {string} md5 of the message
-   * @param type {string} type of the message
    * @param messageDefinition {string} trimmed message definition.
+   * @param topic {string} topic name
+   * @param type {string} type of the message
    *          rosbag relies on this being sent although it is not mentioned in the spec.
    */
-  createPubHeader(callerId, md5sum, type, messageDefinition) {
+  createPubHeader(callerId, md5sum, messageDefinition, topic, type) {
     const fields = [
       callerIdPrefix + callerId,
       md5Prefix + md5sum,
+      messageDefinitionPrefix + messageDefinition,
+      topicPrefix + topic,
       typePrefix + type,
-      messageDefinitionPrefix + messageDefinition
     ];
 
 
@@ -267,7 +269,6 @@ let UdprosUtils = {
     let opCode = buff.readUInt8(4)
     let msgId = buff.readUInt8(5)
     let blkN = buff.readUInt16LE(6)
-
     return {
       connectionId,
       opCode,