I am trying to form FTP connections in C# with unknown IP addresses. How would I check if each address is valid or not?

Question

The following function successfully returns the FTP server's welcome message when the input IP address is valid.

When I test it with something that has the format of an IP address but doesn't correspond to an FTP server, I get a WebException that is thrown from System.dll, and not from the function. The WebException takes a very long time to get caught, and I would like to avoid relying on try-catch if possible.

How would I fix this so when I pass in an invalid IP address, CheckIP returns "Timeout" (or finishes execution in some other way) instead of dealing with the exception?

Note: I'm aware that connections can be tested with Ping, I just wanted to know if there's a way to do it natively within FTP.

public string CheckIP(string ip){
  string respStr="Timeout";
     try
     {
          var connection = (FtpWebRequest)WebRequest.Create(@"ftp://" + ip + @"/");
          connection.Credentials = new NetworkCredential(Username, Password);
          connection.Method = WebRequestMethods.Ftp.PrintWorkingDirectory;
          connection.Timeout = 500;
          var response = (FtpWebResponse)connection.GetResponse();
          respStr = response.WelcomeMessage.ToString();
          response.Close();
      }
      catch (Exception)
      {
          respStr = "Exception";
      }
   return respStr;
}