Unityからchatworkにメッセージを送る

Unityからchatworkにメッセージを送る。(Unity 5.4.0)
適当なオブジェクトにつけてインスペクタからroomidに部屋のID、tokenにAPIトークンを入れる。

using UnityEngine;
using UnityEngine.Networking;
using System.Collections;

public class PostMessage : MonoBehaviour
{
    public string roomid;
    public string token;

    IEnumerator Post(string message)
    {
        string url = string.Format("https://api.chatwork.com/v1/rooms/{0}/messages", roomid);
        WWWForm form = new WWWForm();
        form.AddField("body", message);
        using (UnityWebRequest req = UnityWebRequest.Post(url, form))
        {
            req.SetRequestHeader("X-ChatWorkToken", token);

            yield return req.Send();

            if (req.isError)
            {
                Debug.Log(req.error);
            }
            else
            {
                Debug.Log(req.responseCode);
                Debug.Log(req.downloadHandler.text);
                _message = "";
            }
        }
    }

    string _message = "";

    void OnGUI()
    {
        _message = GUILayout.TextField(_message, GUILayout.Width(200));

        if (GUILayout.Button("Send"))
        {
            StartCoroutine(Post(_message));
        }
    }
}

参考