IsServerRunning — checks whether a server is running at the specified endpoint

test.cs

public static bool IsServerRunning(string url)
{
	if (string.IsNullOrWhiteSpace(url))
	{
		throw new ArgumentNullException("url");
	}

	Uri uri;
	try
	{
		uri = new Uri(url);
	}
	catch (Exception ex)
	{
		throw new ArgumentException("url", ex);
	}

	try
	{
		using (var tcp = new TcpClient())
		{
			tcp.Connect(uri.Host, uri.Port);
			return true;
		}
	}
	catch
	{
		return false;
	}
}

A few notes:

• The method checks whether some server is listening on the given endpoint.
• It doesn't check whether the server implements certain Zyan protocol.
• It doesn't support non-TCP based urls, IPC for example.
• URL prefix is ignored, so it should work with tcp://, tcpex://, http://, whatever.
• The method is kinda slow when the server is not available (has to wait for TCP connect timeout).