[SSDP] add schema(Print &) const (esp8266#6798)

* [SSDP] add `schema(Print &) const`

Supercedes esp8266#2806

Make SSDP::schema(WiFiClient&) use a by-ref (reduce stack use)

Add a SSDP::schema(Print&)

From @Palatis' original PR:
useful when using AsyncWebServer.

* Use ip.toString, only export Print& schema interface

Because WiFiClient inherits a Print interface, replace the
::schema(WiFiClient&) with ::schema(Print&) which is source compatible
with existing code and allows the functionality requested in the initial
PR.

Use ip.toString() in the templates instead of breaking up the octets of
the address.

* Fix compile errors and backwards compatibility

libraries/ESP8266SSDP/ESP8266SSDP.cpp

@@ -73,7 +73,7 @@ static const char _ssdp_packet_template[] PROGMEM =
   "SERVER: Arduino/1.0 UPNP/1.1 %s/%s\r\n" // _modelName, _modelNumber
   "USN: %s\r\n" // _uuid
   "%s: %s\r\n"  // "NT" or "ST", _deviceType
-  "LOCATION: http://%u.%u.%u.%u:%u/%s\r\n" // WiFi.localIP(), _port, _schemaURL
+  "LOCATION: http://%s:%u/%s\r\n" // WiFi.localIP(), _port, _schemaURL
   "\r\n";
 
 static const char _ssdp_schema_template[] PROGMEM =
@@ -88,7 +88,7 @@ static const char _ssdp_schema_template[] PROGMEM =
   "<major>1</major>"
   "<minor>0</minor>"
   "</specVersion>"
-  "<URLBase>http://%u.%u.%u.%u:%u/</URLBase>" // WiFi.localIP(), _port
+  "<URLBase>http://%s:%u/</URLBase>" // WiFi.localIP(), _port
   "<device>"
   "<deviceType>%s</deviceType>"
   "<friendlyName>%s</friendlyName>"
@@ -247,7 +247,7 @@ void SSDPClass::_send(ssdp_method_t method) {
                        _uuid,
                        (method == NONE) ? "ST" : "NT",
                        (_st_is_uuid) ? _uuid : _deviceType,
-                       ip[0], ip[1], ip[2], ip[3], _port, _schemaURL
+                       ip.toString().c_str(), _port, _schemaURL
                       );
 
   _server->append(buffer, len);
@@ -276,12 +276,12 @@ void SSDPClass::_send(ssdp_method_t method) {
   _server->send(remoteAddr, remotePort);
 }
 
-void SSDPClass::schema(WiFiClient client) {
+void SSDPClass::schema(Print &client) const {
   IPAddress ip = WiFi.localIP();
   char buffer[strlen_P(_ssdp_schema_template) + 1];
   strcpy_P(buffer, _ssdp_schema_template);
   client.printf(buffer,
-                ip[0], ip[1], ip[2], ip[3], _port,
+                ip.toString().c_str(), _port,
                 _deviceType,
                 _friendlyName,
                 _presentationURL,

libraries/ESP8266SSDP/ESP8266SSDP.h

@@ -62,7 +62,8 @@ class SSDPClass{
     ~SSDPClass();
     bool begin();
     void end();
-    void schema(WiFiClient client);
+    void schema(WiFiClient client) const { schema((Print&)std::ref(client)); }
+    void schema(Print &print) const;
     void setDeviceType(const String& deviceType) { setDeviceType(deviceType.c_str()); }
     void setDeviceType(const char *deviceType);