Clean code and add example

Author: larsenglund

libraries/ESP8266mDNS/ESP8266mDNS.cpp

@@ -325,36 +325,38 @@ int MDNSResponder::queryService(char *service, char *proto) {
 }
 
 String MDNSResponder::hostname(int idx) {
-  if (_answers == 0) {
+  MDNSAnswer *answer = _getAnswerFromIdx(idx);
+  if (answer == 0) {
     return String();
   }
-  MDNSAnswer *answer = _answers;
-  while (answer != 0 && idx-- > 0) {
-    answer = answer->next;
-  }
   return answer->hostname;
 }
 
 IPAddress MDNSResponder::IP(int idx) {
-  if (_answers == 0) {
+  MDNSAnswer *answer = _getAnswerFromIdx(idx);
+  if (answer == 0) {
     return IPAddress();
   }
-  MDNSAnswer *answer = _answers;
-  while (answer != 0 && idx-- > 0) {
-    answer = answer->next;
-  }
   return IPAddress(answer->ip);
 }
 
 uint16_t MDNSResponder::port(int idx) {
-  if (_answers == 0) {
+  MDNSAnswer *answer = _getAnswerFromIdx(idx);
+  if (answer == 0) {
     return 0;
   }
+  return answer->port;
+}
+
+MDNSAnswer* MDNSResponder::_getAnswerFromIdx(int idx) {
   MDNSAnswer *answer = _answers;
   while (answer != 0 && idx-- > 0) {
     answer = answer->next;
   }
-  return answer->port;
+  if (idx > 0) {
+    return 0;
+  }
+  return answer;
 }
 
 MDNSTxt * MDNSResponder::_getServiceTxt(char *name, char *proto){
@@ -577,8 +579,6 @@ void MDNSResponder::_parsePacket(){
         }
       }
 
-      Serial.printf("Parts collected: %02x\n", partsCollected);
-
       if ((partsCollected == 0x0F) && serviceMatch) {
 #ifdef MDNS_DEBUG_RX
         Serial.println("All answers parsed, adding to _answers list..");

libraries/ESP8266mDNS/ESP8266mDNS.h

@@ -123,6 +123,7 @@ class MDNSResponder {
   void _parsePacket();
   void _reply(uint8_t replyMask, char * service, char *proto, uint16_t port);
   size_t advertiseServices(); // advertise all hosted services
+  MDNSAnswer* _getAnswerFromIdx(int idx);
 };
 
 extern MDNSResponder MDNS;

libraries/ESP8266mDNS/examples/mDNS-SD_Extended/mDNS-SD_Extended.ino

@@ -0,0 +1,75 @@
+/*
+  ESP8266 mDNS-SD responder and query sample
+
+  This is an example of announcing and finding services.
+  
+  Instructions:
+  - Update WiFi SSID and password as necessary.
+  - Flash the sketch to two ESP8266 boards
+  - The last one powered on should now find the other.
+ */
+
+#include <ESP8266WiFi.h>
+#include <ESP8266mDNS.h>
+
+const char* ssid     = "...";
+const char* password = "...";
+char hostString[16] = {0};
+
+void setup() {
+  Serial.begin(115200);
+  delay(100);
+  Serial.println("\r\nsetup()");
+
+  sprintf(hostString, "ESP_%06X", ESP.getChipId());
+  Serial.print("Hostname: ");
+  Serial.println(hostString);
+  WiFi.hostname(hostString);
+
+  WiFi.begin(ssid, password);
+  while (WiFi.status() != WL_CONNECTED) {
+    delay(250);
+    Serial.print(".");
+  }
+  Serial.println("");
+  Serial.print("Connected to ");
+  Serial.println(ssid);
+  Serial.print("IP address: ");
+  Serial.println(WiFi.localIP());
+
+ if (!MDNS.begin(hostString)) {
+    Serial.println("Error setting up MDNS responder!");
+  }
+  Serial.println("mDNS responder started");
+  MDNS.addService("esp", "tcp", 8080); // Announce esp tcp service on port 8080
+
+  Serial.println("Sending mDNS query");
+  int n = MDNS.queryService("esp", "tcp"); // Send out query for esp tcp services
+  Serial.println("mDNS query done");
+  if (n == 0) {
+    Serial.println("no services found");
+  }
+  else {
+    Serial.print(n);
+    Serial.println(" service(s) found");
+    for (int i = 0; i < n; ++i) {
+      // Print details for each service found
+      Serial.print(i + 1);
+      Serial.print(": ");
+      Serial.print(MDNS.hostname(i));
+      Serial.print(" (");
+      Serial.print(MDNS.IP(i));
+      Serial.print(":");
+      Serial.print(MDNS.port(i));
+      Serial.println(")");
+    }
+  }
+  Serial.println();
+  
+  Serial.println("loop() next");
+}
+
+void loop() {
+  // put your main code here, to run repeatedly:
+
+}