POST http client example (#2704)

* POST http client example

* avoid deprecated api

* Update PostHttpClient.ino

style, comments

* Update PostHttpClient.ino

libraries/ESP8266HTTPClient/examples/PostHttpClient/PostHttpClient.ino

@@ -0,0 +1,84 @@
+/**
+   PostHTTPClient.ino
+
+    Created on: 21.11.2016
+
+*/
+
+#include <ESP8266WiFi.h>
+#include <ESP8266HTTPClient.h>
+
+#define USE_SERIAL Serial
+
+/* this can be run with an emulated server on host:
+        cd esp8266-core-root-dir
+        cd tests/host
+        make ../../libraries/ESP8266WebServer/examples/PostServer/PostServer
+        bin/PostServer/PostServer
+   then put your PC's IP address in SERVER_IP below, port 9080 (instead of default 80):
+*/
+//#define SERVER_IP "10.0.1.7:9080" // PC address with emulation on host
+#define SERVER_IP "192.168.1.42"
+
+#ifndef STASSID
+#define STASSID "your-ssid"
+#define STAPSK  "your-password"
+#endif
+
+void setup() {
+
+  USE_SERIAL.begin(115200);
+
+  USE_SERIAL.println();
+  USE_SERIAL.println();
+  USE_SERIAL.println();
+
+  WiFi.begin(STASSID, STAPSK);
+
+  while (WiFi.status() != WL_CONNECTED) {
+    delay(500);
+    USE_SERIAL.print(".");
+  }
+  USE_SERIAL.println("");
+  USE_SERIAL.print("Connected! IP address: ");
+  USE_SERIAL.println(WiFi.localIP());
+
+}
+
+void loop() {
+  // wait for WiFi connection
+  if ((WiFi.status() == WL_CONNECTED)) {
+
+    WiFiClient client;
+    HTTPClient http;
+
+    USE_SERIAL.print("[HTTP] begin...\n");
+    // configure traged server and url
+    http.begin(client, "http://" SERVER_IP "/postplain/"); //HTTP
+    http.addHeader("Content-Type", "application/json");
+
+    USE_SERIAL.print("[HTTP] POST...\n");
+    // start connection and send HTTP header and body
+    int httpCode = http.POST("{\"hello\":\"world\"}");
+
+    // httpCode will be negative on error
+    if (httpCode > 0) {
+      // HTTP header has been send and Server response header has been handled
+      USE_SERIAL.printf("[HTTP] POST... code: %d\n", httpCode);
+
+      // file found at server
+      if (httpCode == HTTP_CODE_OK) {
+        const String& payload = http.getString();
+        USE_SERIAL.println("received payload:\n<<");
+        USE_SERIAL.println(payload);
+        USE_SERIAL.println(">>");
+      }
+    } else {
+      USE_SERIAL.printf("[HTTP] POST... failed, error: %s\n", http.errorToString(httpCode).c_str());
+    }
+
+    http.end();
+  }
+
+  delay(10000);
+}