Merge pull request arduino-libraries#116 from luigigubello/random_local_port

Added method to set random local port

Author: aentinger

NTPClient.cpp

@@ -73,7 +73,7 @@ void NTPClient::begin() {
   this->begin(NTP_DEFAULT_LOCAL_PORT);
 }
 
-void NTPClient::begin(int port) {
+void NTPClient::begin(unsigned int port) {
   this->_port = port;
 
   this->_udp->begin(this->_port);
@@ -146,7 +146,7 @@ bool NTPClient::forceUpdate() {
 bool NTPClient::update() {
   if ((millis() - this->_lastUpdate >= this->_updateInterval)     // Update after _updateInterval
     || this->_lastUpdate == 0) {                                // Update if there was no update yet.
-    if (!this->_udpSetup) this->begin();                         // setup the UDP client if needed
+    if (!this->_udpSetup || this->_port != NTP_DEFAULT_LOCAL_PORT) this->begin(this->_port); // setup the UDP client if needed
     return this->forceUpdate();
   }
   this->_packetSent = false;
@@ -224,6 +224,7 @@ void NTPClient::sendNTPPacket() {
   memset(this->_packetBuffer, 0, NTP_PACKET_SIZE);
   // Initialize values needed to form NTP request
   // (see URL above for details on the packets)
+
   this->_packetBuffer[0] = 0b11100011;   // LI, Version, Mode
   this->_packetBuffer[1] = 0;     // Stratum, or type of clock
   this->_packetBuffer[2] = 6;     // Polling Interval
@@ -244,3 +245,8 @@ void NTPClient::sendNTPPacket() {
   this->_udp->write(this->_packetBuffer, NTP_PACKET_SIZE);
   this->_udp->endPacket();
 }
+
+void NTPClient::setRandomPort(unsigned int minValue, unsigned int maxValue) {
+  randomSeed(analogRead(0));
+  this->_port = random(minValue, maxValue);
+}

NTPClient.h

@@ -15,7 +15,7 @@ class NTPClient {
 
     const char*   _poolServerName = "pool.ntp.org"; // Default time server
     IPAddress     _poolServerIP;
-    int           _port           = NTP_DEFAULT_LOCAL_PORT;
+    unsigned int  _port           = NTP_DEFAULT_LOCAL_PORT;
     long          _timeOffset     = 0;
     bool          _fractionalTime = false;
 
@@ -48,6 +48,11 @@ class NTPClient {
      */
     void setPoolServerName(const char* poolServerName);
 
+     /**
+     * Set random local port
+     */
+    void setRandomPort(unsigned int minValue, unsigned int maxValue);
+
     /**
      * Starts the underlying UDP client with the default local port
      */
@@ -56,7 +61,7 @@ class NTPClient {
     /**
      * Starts the underlying UDP client with the specified local port
      */
-    void begin(int port);
+    void begin(unsigned int port);
 
     /**
      * This should be called in the main loop of your application. By default an update from the NTP Server is only