“No such host is known” error for new TcpClient socket connection set up using .Net Framework classes

I was trying to create a TcpSocket connection to check for .Net’s SSL certificate validation process and was using the TcpClient constructor of the System.Net.Sockets class.

The constructor has a signature like below:

public TcpClient(string hostname, int port)

The hostname is the DNS name of the remote host to which you intend to connect.

The code I wrote and the error was as below.

TcpClient clientFor = new TcpClient(“https://developers.facebook.com”, 443);

The funny thing is I put the uri for the host name instead of the DNS name L

The fix was simple:

TcpClient clientFor = new TcpClient(“developers.facebook.com”, 443);