I want to get data from my NodeMCU to my android application
There are lots of examples in the internet. Look it up on goolge with something like ESP8266 LED webserver or ESP8266 Blynk. There they are mostly showing how to build this and access to your NodeMcu over e.g. Google Chrome. If you want to do it with your own Android Application it is a little more tricky. Look it up 
here or here.

For sending data from the server to the client you should consider using javascript. here is a example code from my ESP8266 Relais control. I took the code from here and modified it to my preferences.
main:

 #include &lt;ESP8266WiFi.h&gt;
    #include &lt;ESP8266WebServer.h&gt;
    const char* ssid = "SSID";
    const char* password = "PASSWORD";

boolean LEDstate = false;

#include "functions.h"
int LED = 2;
int OUT = 5;

IPAddress ip(10, 0, 0, 99);
IPAddress gateway(10, 0, 0, 1);
IPAddress subnet(255, 255, 255, 0);

void setup() {
    pinMode(LED, OUTPUT);
    Serial.begin(115200); delay(100);
    Serial.print("... Attempting to log into router... \r\n");

    WiFi.begin(ssid, password);

    WiFi.config(ip, gateway, subnet);

    while (WiFi.status() != WL_CONNECTED) delay(500);
    WiFi.mode(WIFI_STA);

    Serial.println("\n\nBOOTING ESP8266 ...");
    Serial.print("Connected to ");
    Serial.println(ssid);
    Serial.println("Station IP address: ");
    Serial.println(WiFi.localIP());

    server.on("/", handleWebsite);
    server.on("/setESPval", handleESPval);
  server.on("/xml", handleXML);
    server.begin();
}

void loop() {
    server.handleClient();
 buildXML();
    delay(100);
    if (LEDstate) {
        digitalWrite(LED, HIGH);
    }
    else {
        digitalWrite(LED, LOW);
    }
}


functions.h

ESP8266WebServer server(80);
String webSite;
String javaScript;
String XML;
void buildJavascript() {
  javaScript = "&lt;SCRIPT&gt;\n";
  javaScript += "xmlHttp=createXmlHttpObject();\n";

  javaScript += "function createXmlHttpObject(){\n";
  javaScript += "  if(window.XMLHttpRequest){\n";
  javaScript += "    xmlHttp=new XMLHttpRequest();\n";
  javaScript += "  }else{\n";
  javaScript += "    xmlHttp=new ActiveXObject('Microsoft.XMLHTTP');\n";
  javaScript += "  }\n";
  javaScript += "  return xmlHttp;\n";
  javaScript += "}\n";

  javaScript += "function process(){\n";
  javaScript += "  if(xmlHttp.readyState==0||xmlHttp.readyState==4){\n";
  javaScript += "    xmlHttp.onreadystatechange=function(){\n";
  javaScript += "      if(xmlHttp.readyState==4&amp;&amp;xmlHttp.status==200){\n";
  javaScript += "        xmlDoc=xmlHttp.responseXML;\n";
  javaScript += "         console.log(xmlDoc.getElementsByTagName('mt')[0]);\n";

  javaScript += "        xmlmsg=xmlDoc.getElementsByTagName('mt')[0].firstChild.nodeValue;\n";
  javaScript += "        document.getElementById('runtime').innerHTML=xmlmsg;\n";
  javaScript += "        xmlmsg=xmlDoc.getElementsByTagName('state')[0].firstChild.nodeValue;\n";
  javaScript += "        document.getElementById('ledstate').innerHTML=xmlmsg;\n";
  javaScript += "      }\n";
  javaScript += "    }\n";
  javaScript += "    xmlHttp.open('PUT','xml',true);\n";
  javaScript += "    xmlHttp.send(null);\n";
  javaScript += "  }\n";
  javaScript += "  setTimeout('process()',1000);\n";
  javaScript += "}\n";

  javaScript += " function sendRequest(nr) {\n";

  //javaScript += "alert(nr);";
  javaScript += "if (xmlHttp.readyState == 0 || xmlHttp.readyState == 4) {\n";
   javaScript += "        xmlDoc=xmlHttp.responseXML;\n";
  javaScript += "        xmlmsg=xmlDoc.getElementsByTagName('mt')[0].firstChild.nodeValue;\n";
  javaScript += "        document.getElementById('runtime').innerHTML=xmlmsg;\n";
  javaScript += "     xmlHttp.open('PUT', 'setESPval?fnc=' + nr, true);\n";
  javaScript += "     xmlHttp.send(null);\n";
  javaScript += "}\n}";
  javaScript += "&lt;/SCRIPT&gt;\n";

  Serial.println("JavaScript built");
}

void buildWebsite() {
  buildJavascript();
  webSite = "&lt;!DOCTYPE HTML&gt;\n";
  webSite += "&lt;META name='viewport' content='width=device-width, initial-scale=1'&gt;\n";
  webSite += javaScript;
    webSite += "&lt;BODY onload='process()'&gt;\n";
  webSite += "Runtime = &lt;A ID='runtime'&gt;&lt;/A&gt;\n";
  webSite += "LEDstate = &lt;A ID='ledstate'&gt;&lt;/A&gt;\n";
  webSite += "&lt;br&gt;&lt;button onclick='sendRequest(0)'&gt;Funktion 1&lt;/button&gt;\n";
  webSite += "&lt;button onclick='sendRequest(1)'&gt;Funktion 2&lt;/button&gt;\n";
  webSite += "&lt;/HTML&gt;\n";

//  webSite += "&lt;!DOCTYPE html&gt;&lt;html&gt;&lt;head&gt;    &lt;title&gt;JavaScript View&lt;/title&gt;    &lt;script type="text/javascript"&gt;        function showToast(){            var message = document.getElementById("message").value;           var lengthLong = document.getElementById("length").checked;           app.makeToast(message, lengthLong);            return false;        }       /*             Call the 'showToast' method when the form gets             submitted (by pressing button or return key on keyboard).          */        window.onload = function(){          var form = document.getElementById("form");            form.onsubmit = showToast;       }   &lt;/script&gt;&lt;/head&gt;&lt;body&gt;&lt;form id="form"&gt;    Message: &lt;input id="message" name="message" type="text"/&gt;&lt;br /&gt;    Long: &lt;input id="length" name="length" type="checkbox" /&gt;&lt;br /&gt;    &lt;input type="submit" value="Make Toast" /&gt;&lt;/form&gt;&lt;/body&gt;&lt;/html&gt;"
  Serial.println("HTML built");
}

String millis2time() {
  String Time = "";
  unsigned long ss;
  byte mm, hh;
  ss = millis() / 1000;
  hh = ss / 3600;
  mm = (ss - hh * 3600) / 60;
  ss = (ss - hh * 3600) - mm * 60;
  if (hh &lt; 10)Time += "0";
  Time += (String)hh + ":";
  if (mm &lt; 10)Time += "0";
  Time += (String)mm + ":";
  if (ss &lt; 10)Time += "0";
  Time += (String)ss;
  return Time;
}

int i = 0;
void buildXML() {
  XML = "&lt;?xml version='1.0'?&gt;";
  XML += "&lt;xml&gt;";
  XML += "&lt;mt&gt;";
  XML += millis2time();
  XML += "&lt;/mt&gt;";
  XML += "&lt;state&gt;";
  XML += LEDstate;
  XML += "&lt;/state&gt;";
  XML += "&lt;/xml&gt;";
  //Serial.println(XML);
}

void handleWebsite() {
  buildWebsite();
  server.send(200, "text/html", webSite);
}

void handleXML() {
  buildXML();
  server.send(200, "text/xml", XML);
  Serial.println("Website handeled");
}


void handleESPval() {
  //Serial.println("HANDLE");
  if (server.arg("fnc").toInt() == 0) {
    Serial.println("BTN1 pressed");
    delay(100);
    LEDstate = false;
  }
  else if (server.arg("fnc").toInt() == 1) {
    Serial.println("BTN2 pressed");
    delay(100);
    LEDstate = true;
  }
  Serial.println(LEDstate);
  server.send(200, "text/xml", XML);
}