Fix issue espressif#5507 "Constructor WebServer::WebServer(IPAddress addr, int port) produces an unexpected result"

This change adds support for multi-homed servers to libraries/WiFi.  It was assumed to be there already by libraries/WebServer, but was not.
This led to unexpected results when the IP address-specific constructor of class WebServer was used (see issue 5507).

This change was tested using three concurrent instances of WebServer, one bound to the WiFi station address, one bound to the WiFi soft AP address,
and one bound to INADDR_ANY.  See libraries/WebServer/examples/MultiHomedServers for the test method.

Author: timr49

Diff for: libraries/WebServer/examples/MultiHomedServers/.gitignore

@@ -0,0 +1 @@
+secret.h

Diff for: libraries/WebServer/examples/MultiHomedServers/MultiHomedServers.ino

@@ -0,0 +1,174 @@
+#include <WiFi.h>
+#include <WiFiClient.h>
+#include <WebServer.h>
+#include <ESPmDNS.h>
+
+/*
+ * MultiHomedServers
+ * 
+ * MultiHomedServers tests support for multi-homed servers, i.e. a distinct web servers on each IP interface. 
+ * It only tests the case n=2 because on a basic ESP32 device, we only have two IP interfaces, namely
+ * the WiFi station interfaces and the WiFi soft AP interface.
+ *
+ * For this to work, the WebServer and the WiFiServer classes must correctly handle the case where an 
+ * IP address is passed to their relevant constructor. It also requires WebServer to work with multiple,
+ * simultaneous instances.
+ * 
+ * Testing the WebServer and the WiFiServer constructors was the primary purpose of this script.
+ * The part of WebServer used by this sketch does seem to work with multiple, simultaneous instances.
+ * However there is much functionality in WebServer that is not tested here. It may all be well, but
+ * that is not proven here.
+ * 
+ * This sketch starts the mDNS server, as did HelloServer, and it resolves esp32.local on both interfaces,
+ * but was not otherwise tested.
+ * 
+ * This script also tests that a server not bound to a specific IP address still works.
+ * 
+ * We create three, simultaneous web servers, one specific to each interface and one that listens on both:
+ * 
+ *  name    IP Address      Port
+ *  ----    ----------      ----
+ *  server0 INADDR_ANY      8080
+ *  server1 station address 8081
+ *  server2 soft AP address 8082
+ *  
+ *  The expected responses to a brower's requests are as follows:
+ *  
+ *  1. when client connected to the same WLAN as the station:
+ *      Request URL                 Response
+ *      -----------                 --------
+ *      http://stationaddress:8080  "hello from server0"
+ *      http://stationaddress:8081  "hello from server1"
+ *      http://stationaddress:8082  browser reports failure to connect
+ *      
+ *  2. when client is connected to the soft AP:
+ *  
+ *      Request URL                 Response
+ *      -----------                 --------
+ *      http://softAPaddress:8080   "hello from server0"
+ *      http://softAPaddress:8082   "hello from server2"
+ *      http://softAPaddress:8081   browser reports failure to connect
+ *
+ *  3. Repeat 1 and 2 above with esp32.local in place of stationaddress and softAPaddress, respectively.
+ *  
+ * MultiHomedServers was originally based on HelloServer.
+ */
+
+#include "secret.h"
+const char* ssid = MySSID;
+const char* password = MyPASSWORD;
+const char *apssid = "ESP32";
+
+WebServer *server0, *server1, *server2;
+
+const int led = 13;
+
+void handleRoot(WebServer *server, const char *content) {
+  digitalWrite(led, 1);
+  server->send(200, "text/plain", content);
+  digitalWrite(led, 0);
+}
+
+void handleRoot0() {
+  handleRoot(server0, "hello from server0");
+}
+
+void handleRoot1() {
+  handleRoot(server1, "hello from server1");
+}
+
+void handleRoot2() {
+  handleRoot(server2, "hello from server2");
+}
+
+void handleNotFound(WebServer *server) {
+  digitalWrite(led, 1);
+  String message = "File Not Found\n\n";
+  message += "URI: ";
+  message += server->uri();
+  message += "\nMethod: ";
+  message += (server->method() == HTTP_GET) ? "GET" : "POST";
+  message += "\nArguments: ";
+  message += server->args();
+  message += "\n";
+  for (uint8_t i = 0; i < server->args(); i++) {
+    message += " " + server->argName(i) + ": " + server->arg(i) + "\n";
+  }
+  server->send(404, "text/plain", message);
+  digitalWrite(led, 0);
+}
+
+void handleNotFound0() {
+  handleNotFound(server0);
+}
+
+void handleNotFound1() {
+  handleNotFound(server1);
+}
+
+void handleNotFound2() {
+  handleNotFound(server2);
+}
+
+void setup(void) {
+  pinMode(led, OUTPUT);
+  digitalWrite(led, 0);
+  Serial.begin(115200);
+  WiFi.mode(WIFI_STA);
+  WiFi.begin(ssid, password);
+  Serial.println("");
+
+  // Wait for connection
+  while (WiFi.status() != WL_CONNECTED) {
+    delay(500);
+    Serial.print(".");
+  }
+  Serial.println("");
+  Serial.print("Connected to ");
+  Serial.println(ssid);
+  Serial.print("IP address: ");
+  Serial.println(WiFi.localIP());
+  if (!WiFi.softAP(apssid)) {
+    Serial.println("failed to start softAP");
+    for (;;) {
+        digitalWrite(led, 1);
+        delay(100);
+        digitalWrite(led, 0);
+        delay(100);
+    }
+  }
+  Serial.print("Soft AP: ");
+  Serial.print(apssid);
+  Serial.print(" IP address: ");
+  Serial.println(WiFi.softAPIP());
+
+  if (MDNS.begin("esp32")) {
+    Serial.println("MDNS responder started");
+  }
+
+  server0 = new WebServer(8080);
+  server1 = new WebServer(WiFi.localIP(), 8081);
+  server2 = new WebServer(WiFi.softAPIP(), 8082);
+
+  server0->on("/", handleRoot0);
+  server1->on("/", handleRoot1);
+  server2->on("/", handleRoot2);
+
+  server0->onNotFound(handleNotFound0);
+  server1->onNotFound(handleNotFound1);
+  server2->onNotFound(handleNotFound2);
+
+  server0->begin();
+  Serial.println("HTTP server0 started");
+  server1->begin();
+  Serial.println("HTTP server1 started");
+  server2->begin();
+  Serial.println("HTTP server2 started");
+}
+
+void loop(void) {
+  server0->handleClient();
+  server1->handleClient();
+  server2->handleClient();
+  delay(2);//allow the cpu to switch to other tasks
+}

Diff for: libraries/WebServer/src/WebServer.cpp

@@ -59,6 +59,7 @@ WebServer::WebServer(IPAddress addr, int port)
 , _contentLength(0)
 , _chunked(false)
 {
+  log_v("WebServer::Webserver(addr=%s, port=%d)", addr.toString().c_str(), port);
 }
 
 WebServer::WebServer(int port)
@@ -81,6 +82,7 @@ WebServer::WebServer(int port)
 , _contentLength(0)
 , _chunked(false)
 {
+  log_v("WebServer::Webserver(port=%d)", port);
 }
 
 WebServer::~WebServer() {
@@ -289,7 +291,7 @@ void WebServer::handleClient() {
       return;
     }
 
-    log_v("New client");
+    log_v("New client: client.localIP()=%s", client.localIP().toString().c_str());
 
     _currentClient = client;
     _currentStatus = HC_WAIT_READ;

Diff for: libraries/WiFi/src/WiFiServer.cpp

@@ -82,7 +82,7 @@ void WiFiServer::begin(uint16_t port, int enable){
     return;
   setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(int));
   server.sin_family = AF_INET;
-  server.sin_addr.s_addr = INADDR_ANY;
+  server.sin_addr.s_addr = _addr;
   server.sin_port = htons(_port);
   if(bind(sockfd, (struct sockaddr *)&server, sizeof(server)) < 0)
     return;

Diff for: libraries/WiFi/src/WiFiServer.h

@@ -22,11 +22,14 @@
 #include "Arduino.h"
 #include "Server.h"
 #include "WiFiClient.h"
+#include "arpa/inet.h"
+#include "IPAddress.h"
 
 class WiFiServer : public Server {
   private:
     int sockfd;
     int _accepted_sockfd = -1;
+    IPAddress _addr;
     uint16_t _port;
     uint8_t _max_clients;
     bool _listening;
@@ -35,7 +38,12 @@ class WiFiServer : public Server {
   public:
     void listenOnLocalhost(){}
 
-    WiFiServer(uint16_t port=80, uint8_t max_clients=4):sockfd(-1),_accepted_sockfd(-1),_port(port),_max_clients(max_clients),_listening(false),_noDelay(false){}
+    WiFiServer(uint16_t port=80, uint8_t max_clients=4):sockfd(-1),_accepted_sockfd(-1),_addr(INADDR_ANY),_port(port),_max_clients(max_clients),_listening(false),_noDelay(false) {
+      log_v("WiFiServer::WiFiServer(port=%d, ...)", port);
+    }
+    WiFiServer(const IPAddress& addr, uint16_t port=80, uint8_t max_clients=4):sockfd(-1),_accepted_sockfd(-1),_addr(addr),_port(port),_max_clients(max_clients),_listening(false),_noDelay(false) {
+      log_v("WiFiServer::WiFiServer(addr=%s, port=%d, ...)", addr.toString().c_str(), port);
+    }
     ~WiFiServer(){ end();}
     WiFiClient available();
     WiFiClient accept(){return available();}