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We will use web servers in our example as you all know that a web server is a computer running an application that allows other computers to connect to it and retrieve the web pages stored there. Therefore, I will give you an example of how this works in real life so you can have a better understanding. This all probably still feels confusing to you, and there is nothing wrong with that, as this is a complicated concept to grasp. Note that once an application binds itself to a particular port, that port can not be used by any other application. Figure 1, below, is a represenation of an IP address split into its many TCP and UDP ports. If it uses the UDP protocol to send and receive data, it will use a UDP port. If it uses the TCP protocol to send and receive the data then it will connect and bind itself to a TCP port. When a program on your computer sends or receives data over the Internet it sends that data to an ip address and a specific port on the remote computer, and receives the data on a usually random port on its own computer. You can have a total of 65,535 TCP Ports and another 65,535 UDP ports. You have an IP address, and then many ports on that IP address. The cable company knows how to send cable to your cable box based upon a unique serial number associated with that box (IP Address), and then you receive the individual shows on different channels (Ports). When information is sent over the Internet to your computer how does your computer accept that information? It accepts that information by using TCP or UDP ports.Īn easy way to understand ports is to imagine your IP address is a cable box and the ports are the different channels on that cable box. This IP address is used to recognize your particular computer out of the millions of other computers connected to the Internet. Lets move on to the next section where we can describe the concept of ports better.Īs you know every computer or device on the Internet must have a unique number assigned to it called the IP address. Now that you understand what TCP and UDP are, we can start discussing TCP and UDP ports in detail. Most of the time they do, but sometimes it gets lost along the way. You place your mail in the mailbox and hope the Postal Service will get it to the proper location. A comparison you can use for this method is the plain old US Postal Service. On the other hand, this method of transmission has a very low overhead and is therefore very popular to use for services that are not that important to work on the first try. This method of transmission does not provide any guarantee that the data you send will ever reach its destination. What this means is that UDP does not connect directly to the receiving computer like TCP does, but rather sends the data out and relies on the devices in between the sending computer and the receiving computer to get the data where it is supposed to go properly. Using this method, the computer sending the data packages the information into a nice little package and releases it into the network with the hopes that it will get to the right place. You have a conversation and when it is over, you both hang up, releasing the connection. A real life comparison to this method would be to pick up the phone and call a friend. This method of transferring data tends to be quicker and more reliable, but puts a higher load on the computer as it has to monitor the connection and the data going across it. With this method, the two computers can guarantee that the data has arrived safely and correctly, and then they disconnect the connection. Using this method, the computer sending the data connects directly to the computer it is sending the data it to, and stays connected for the duration of the transfer. TCP stands for Transmission Control Protocol. UDP? TCP? I know you are getting confused, but I promise I will explain this in very basic terms so that you can understand this concept. That information is sent most often via two methods, UDP and TCP. When a computer in New York wants to send a piece of data to a computer in England, it must know the destination IP address that it woud like to send the information to. The devices and comptuers connected to the Internet use a protocol called TCP/IP to communicate with each other. If you understand the concepts of IP addresses, then lets move on to TCP and UDP ports and how they work. If you have not read our article on IP addresses and need a brush up, you can find the article here. In this tutorial we will discuss the concept of Ports and how they work with IP addresses.
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