REST in Unity (send messages from webserver to unity)

Question

Is there a way to have a simple webserver send messages to Unity?

At the moment, we're doing a GET using UnityWebRequest.Get() in the update method. Here's the code:

// Update is called once per frame
void Update () {
    StartCoroutine(GetData());
}

IEnumerator GetData()
{
    UnityWebRequest uwr = UnityWebRequest.Get(url);
    yield return uwr.Send();

    if (uwr.isError)
    {
        Debug.Log(uwr.error);
    }else
    {
        Debug.Log((float.Parse(uwr.downloadHandler.text) / 100));
        fnumber = ((float.Parse(uwr.downloadHandler.text) / 100));
        transform.position.Set(oldX, fnumber, oldZ);
    }
}

However, this throws this error:

CANNOT RESOLVE DESTINATION HOST

I found this bug-report, which states, it would have been fixed, which doesn't seem so.

So, is there a way to have the server send messages to Unity?

Thanks

Seasickness

Why don't you just open up socket connection on a different thread and feed your Unity's thread with some delegates? – Livre

Sorry, could you explain this a little deeper? Would be great. – Seasickness

Just create a Thread and use Socket inside to connect to your web server. Then in your Thread' s main method simply send/receive data and transmit them to other parts of your application. – Livre

Why would you need to call this in update? You'll run like hundreds of coroutines at the same time. This can be a reason. – Cano

Because we need to get the data as often as possible. – Seasickness

Check m.rogalski's answer. That will likely solve your problem. What happens when you call that function from the Start function only. Is it throwing the-same error? – Catcall

Answer 1

Expanding my comment to be more descriptive and concrete, my suggestion is to create a simple Thread that will serve as the communication manager with your server.

First of all you have to implement this class to call methods on Unity's UI thread.

When you implement this just create a class :

public class CommunicationManager
{
    static readonly object syncRoot = new object();

    static CommunicationManager _Instance;
    public static CommunicationManager Instance
    {
        get
        {
            if ( _Instance == null )
            {
                lock ( syncRoot )
                {
                    if ( _Instance == null )
                    {
                        _Instance = new CommunicationManager();
                    }
                }
            }
            return _Instance;
        }
    }

    volatile bool working = false;

    Queue<Message> _messages;

    private CommunicationManager()
    {
        _messages = new Queue<Message>();
        InitializeCommunication();
    }

    void InitializeCommunication()
    {
        Thread t = new Thread(CommunicationLoop);
        t.Start();
    }

    void CommunicationLoop()
    {
        Socket s = null;
        try
        {
            Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            s.Connect(new IPEndPoint(IPAddress.Parse("127.0.0.1"), 1337));
            working = true;
        }
        catch(Exception ex)
        {
            working = false;
        }
        while ( working )
        {
            lock ( syncRoot )
            {
                while ( _messages.Count > 0 )
                {
                    Message message = _messages.Dequeue();
                    MessageResult result = message.Process(s);
                    result.Notify();
                }
            }
            Thread.Sleep(100);
        }
    }

    public void EnqueueMessage(Message message)
    {
        lock ( syncRoot )
        {
            _messages.Enqueue( message );
        }
    }
}

Now you have to make Message and MessageResult objects :

public class Message
{
    const string REQUEST_SCHEME = "{0} {1} HTTP/1.1\r\nHost: {hostname}\r\nContent-Length: 0\r\n\r\n";
    string request;
    Action<MessageResult> whenCompleted;

    public Message(string requestUri, string requestType, Action<MessageResult> whenCompleted)
    {
        request = string.Format(REQUEST_SCHEME, requestType, requestUri);
        this.whenCompleted = whenCompleted;
    }

    public MessageResult Process(Socket s)
    {
        IPEndPoint endPoint = (IPEndPoint)s.RemoteEndPoint;
        IPAddress ipAddress = endPoint.Address;
        request = request.Replace("{hostname}", ipAddress.ToString());
        s.Send(Encoding.UTF8.GetBytes(request));

        // receive header here which should look somewhat like this :
        /*
                HTTP/1.1 <status>
                Date: <date>
                <some additional info>
                Accept-Ranges: bytes
                Content-Length: <CONTENT_LENGTH>
                <some additional info>
                Content-Type: <content mime type>
         */
         // when you receive this all that matters is <CONTENT_LENGTH>
         int contentLength = <CONTENT_LENGTH>;
         byte[] msgBuffer = new byte[contentLength];
         if (s.Receive(msgBuffer) != contentLength )
         {
             return null;
         }

         return new MessageResult(msgBuffer, whenCompleted);
    }
}

And lastly create MessageResult object :

public class MessageResult
{
    Action<MessageResult> notifier;
    byte[] messageBuffer;

    public MessageResult(byte[] message, Action<MessageResult> notifier)
    {
        notifier = notifier;
        messageBuffer = message;
    }

    public void Notify()
    {
        UnityThread.executeInUpdate(() =>
        {
            notifier(this);
        });
    }
}

This method will run aside from your main application so that wont produce any freezes and whatever.

To use this you can just call something like this :

Message message = new Message("/index.html", "GET", IndexDownloaded);
CommunicationManager.Instance.EnqueueMessage(message);

// ...
public void IndexDownloaded(MessageResult result)
{
    // result available here
}

For more informations read this wikipedia article about HTTP.

Livre

I like this. Is this the only workaround? Instead of rolling your own webrequest, Can't HttpWebRequest solve this problem? – Catcall

I think you can use HttpWebRequest too but haven't checked that so I couldn't use it in my answer. :) – Livre

Answer 2

This is simple way to get request from RESTful server :D.

private string m_URL = "https://jsonblob.com/api/d58d4507-15f7-11e7-a0ba-014f05ea0ed4";

IEnumerator Start () {
    var webRequest = new WWW (m_URL);
    yield return webRequest;
    if (webRequest.error != null) {
        Debug.Log (webRequest.error);
    } else {
        Debug.Log (webRequest.text);
    }
}

Hispaniola

Answer 3

Try to use the WWW call instead the UnityWebRequest which is broken. What version of unity are you using ?

Cottle

If you know exact bugs - please let me know what they are. As I have been using it UnityWebRequest in production for a while now serving millions of requests and there was no problems with it. – Cano

The latest version – Seasickness