In order to establish a TCP/IP connection you need to do the following.

• Prior to anything happening, there needs to be some agreement on the form of the data.
• In HTML web pages there is a string "http" that is often used.  It means "HyperText Transfer Protocol".  What that means is that there is an agreement on the format of the file that will be transferred from the server to the client and how that file will be interpreted.
• There are other protocols that have been use - and are still used.  One of those is "ftp" for "File Transfer Protocol" which has been used for simple file transfers.
• The server must "listen" for a connection.  In other words, the server must determine when a request has come from a possible client.  That address has to be sent to the correct IP address and the correct port on the server computer.
• When the server receives a request, a connection is established.  The phraseology is that a connection is "opened".
• After the connection is established, the server needs to prepare the data for transmission in the agreed-upon format.
• Then the server needs to send the data.
• When everything is complete, the server closes the connection.

• Things can happen.  For example, the client computer can crash and the data may not get to the client.  When that happens, the connection should terminate gracefully.  (It shouldn't cause any problems at the server, in other words.)
• There absolutely, positively must be an agreement - referred to as a "protocol" - between the server and the client.  In many cases, a standard protocol - like http - is used, but that does not eliminate the possibility of a unique protocol for your situation.  Simple data servers - like a server giving stock quotes - can use very simple protocols.  Over time, the http protocol has expanded to include many things beyond what was in the original version of HTML.