3-way handshake

• This request contains something called a SYN (short for synchronise) bit, which essentially makes first contact in starting the connection process.
• The server will then respond with a packet containing the SYN bit, as well as another "acknowledgement" bit, called ACK.
• Finally, your computer will send a packet that contains the ACK bit by itself, confirming that the connection has been setup successfully.

If the server is respond with an RST.

• Could be closed, filtered, blocked by the Firewall or another reason.