无法使用角度4中的远程api发送登录请求

Question

我正在尝试以角度4进行远程登录请求，但是表单提交无法发送，而不是发送请求到localhost。

    <form class="form-signin" (ngSubmit)="f.form.valid && login()" #f="ngForm">
      <h2 class="form-signin-heading">Log In</h2>
      <label for="inputEmail" class="sr-only">Email</label>
      <input type="email" id="inputEmail" class="form-control" [(ngModel)]="user.email" name="email" placeholder="Email" required autofocus>
      <label for="inputPassword" class="sr-only">Password</label>
      <input type="password" id="inputPassword" class="form-control" [(ngModel)]="user.password" name="password" placeholder="Password" required>
      <button class="btn btn-lg btn-primary btn-block" type="submit">Log in</button>
    </form>


#login.component.ts
login() {
    this.authenticationService.login(this.user).subscribe(
        data => {
          console.log(data)
      },
        error => {
          console.log(error)
      });
  }


#authentication.service.ts
login(user) {
    return this.http.post('http://192.168.6.24:3000/token', JSON.stringify({ username: user.email, password: user.password }))
      .map((response: Response) => {

        let user = response.json();
        if (user && user.token) {       
          console.log(user);
        }

        return user;
      });
  }