Unity's TCP socket connection attempt "actively refused"

Questions & Answers
1

I’m trying to read data from a Java service on an Android device. But Unity always refuses to connect to the TCP socket. It refuses in the editor, it refuses on Android and it refuses if I try to build for Windows. In the Editor, it says: System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it.

My code is below. It’s a adapted from an example from a Microsoft API page. uPrint is a function I wrote to print text both in the console and in a GUIText.

The code is called with:

Connect("127.0.0.1", "Hello!");

I’ve tried "0.0.0.0" and "localhost" for the host name. It didn’t work.

I haven’t found a way to get at which line exactly the error occurs. Even removing the try/catch blocks does not give me the exact line where it fails.

The Windows firewall allows the Unity editor full access to the network.

	void Connect(string server, string message) {
		try {
			// Create a TcpClient. 
			// Note, for this client to work you need to have a TcpServer  
			// connected to the same address as specified by the server, port 
			// combination.
			int port = 15219;
			TcpClient client = new TcpClient(server, port);
			
			// Translate the passed message into ASCII and store it as a Byte array.
			byte[] data = System.Text.Encoding.ASCII.GetBytes(message);         
			
			// Get a client stream for reading and writing. 
			// Stream stream = client.GetStream(); // GetStream();
			
			NetworkStream stream = client.GetStream();
			
			// Send the message to the connected TcpServer. 
			// stream.Write(data, 0, data.Length);
			
			uPrint(string.Format("Sent: {0}", message));
			
			// Receive the TcpServer.response. 
			
			// Buffer to store the response bytes.
			data = new Byte[256];
			
			// String to store the response ASCII representation.
			string responseData = string.Empty;
			
			// Read the first batch of the TcpServer response bytes.
			int bytes = stream.Read(data, 0, data.Length);
			responseData = System.Text.Encoding.ASCII.GetString(data, 0, bytes);
			uPrint(string.Format("Received: {0}", responseData));
			
			// Close everything.
			stream.Close();         
			client.Close();         
		} 
		catch (ArgumentNullException e) {
			uPrint(string.Format("ArgumentNullException: {0}", e));
		}
		catch (SocketException e) {
			uPrint(string.Format("SocketException: {0}", e));
		}		
	}
2

Well, do you have any other software that can connect to your “Java service”? TCP socket connections have to be accepted on the server. When you “connect” you just send a connection request to the server socket. The server has to call accept which will open another socket for the client. It seems your server doesn’t do this maybe due to security settings. I’m pretty sure it has nothing to do with the way you connect.

3

@eje211 The Reason your have the actively refused connection problem is because you’re probably not using your external Ip and you probably don’t have the port forwarded to you computer in your router. Because if you don’t have the port forwarded to your router then you can’t send and receive messages to other clients.

4

I had the same problem and found out it was unity blocking it.
Heres how to stop unity from blocking it.

void Connect()
{
      //need to tell unity to let me use the port im about to use
      Security.PrefetchSocketPolicy(IP,PORT); 
      //now I can connect to my server
      ClientSocket.Connect(IP, PORT);
}