app-settings.ts

import { Injectable } from '@angular/core';

@Injectable()
export class AppSettingsProvider {

  endPoint: string;
  baseUrl: string;
  mode: string;

  constructor() {
    let domain = "http://192.168.1.4:3000/";
    // let domain = "http://2a2cb1ba.ngrok.io/";

    // this.mode = 'browser'; // mobile if on mobile mode
    this.mode = 'mobile';

    this.endPoint = domain;
    this.baseUrl = domain;
  }

}

control.ts

import { Http } from "@angular/http";
import { Injectable } from '@angular/core';
import { AppSettingsProvider } from '../app-settings/app-settings';

@Injectable()
export class ControlsProvider {

  constructor(
    public http: Http,
    public appSettings: AppSettingsProvider
  ) {}

  getDeviceList() {
    let url = this.appSettings.endPoint + "devices.json";

    return new Promise((resolve, reject) => {
      this.http.get(url).subscribe(
        res => {
          resolve(res.json());
        },
        err => {
          reject(err);
        }
      );
    });
  }
}