import { Injectable } from '@angular/core';
import { Subject } from 'rxjs/Subject';
@Injectable()
export class SharedService {
 // Observable string sources
 private emitChangeSource = new Subject<any>();
 // Observable string streams
 changeEmitted$ = this.emitChangeSource.asObservable();
 // Service message commands
 emitChange(change: any) {
 this.emitChangeSource.next(change);
 }
}

import { Component} from '@angular/core';
@Component({
 templateUrl: 'child.html',
 styleUrls: ['child.scss']
})
export class ChildComponent {
 constructor(
 private _sharedService: SharedService
 ) { }
onClick(){
 this._sharedService.emitChange('Data from child');
 }
}

import { Component} from '@angular/core';
@Component({
 templateUrl: 'parent.html',
 styleUrls: ['parent.scss']
})
export class ParentComponent {
 constructor(
 private _sharedService: SharedService
 ) {
 _sharedService.changeEmitted$.subscribe(
 text => {
 console.log(text);
 });
 }
}