Transmission Control Protocol
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The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. TCP is suitable for applications like file transfer and E-mail, because it provides reliable, in-order delivery of a stream of bytes. Sometimes the entire suite is referred to as 'the TCP/IP protocol suite' due to its importance in the Internet protocol. TCP is the transport protocol that manages the individual conversations between web servers and clients. TCP divides the HTTP messages into smaller pieces to be sent to the destination. It is also responsible for controlling the size and rate at which messages are exchanged between the server and client.
The Internet Protocol (IP) works by exchanging packages (groups of information). Packets are short sequences of bytes consisting of a header and a body. The header describes the packet's destination and helps pass the packet between routers until it arrives at its final destination. The body contains the application data.
TCP is used by the World Wide Web, E-mail, File Transfer Protocol (FTP), Secure Shell, and some streaming media applications. It consists of a set of rules, the protocol, that are used with the IP (Internet Protocol) to send data “in a form of message units” between computers via the Internet. Simultaneously, the IP handles the actual delivery of the data and the TCP keeps track of the individual units of data “packets” that a message is divided into.
How TCP Works
An HTML file is sent to you from a Web server. The TCP program layer of that server takes the file as a stream of bytes and divides it into packets, numbers them, and forwards them individually to the IP program layer. Even though every packet has the same destination IP address, ackets can get routed differently through the network, so when the client program in your computer gets them, the TCP stack (implementation) reassembles the individual packets and ensures they are correctly ordered as it streams them to an application.
A list of the most common TCP ports is available in this article: List of TCP and UDP Ports
