This will be the port number used at the SERVER end of the connection, but what should the port number be on your computer (the client) when making this connection? When an application is finished using an ephemeral port, it is returned to the operating system's pool of available ports, and is available for reuse by the same application later, or another application.Īgain, because the operating system is managing this pool of ephemeral ports, applications don't need to worry about this allocation and deallocation process, they simply get one when needed.įor example, if you open your browser application and connect to the browser will connect to the IP address associated with on port 80 (the HTTP protocol port). This means that when using ephemeral ports, the numeric port number assigned by the operating system is decided dynamically at the time of the request. It's basically like asking the Operating System to choose a number it wishes to use, and removes the burden of tracking which ones are being used away from the application. These ports are used when an application wants to make a network connection, but doesn't need to assign that connection to a specific port number. This article is not designed to be an exhaustive description of network programming, but an overview of why network port numbers need some consideration.Įphemeral ports are managed internally by the operating system, whether that be Linux, Windows or any other operating system that is capable of network communication. For the most part, these are both independent and do not interfere with each other, so it is possible for a UDP connection and a TCP connection from two different applications to share the same numeric port number without interference, although we encourage readers to avoid complicating their configurations wherever possible. This is either a specifically assigned numeric value, or a value that is assigned dynamically by the operating system, as an ephemeral port, described below.Īn odd complication exists where network connection types can be either TCP or UDP. Generally for every connection into and out of a server, a network port is needed. When you open your browser and go to you are actually opening a connection to port 80 (the phone number) within the LumenVox web server (the exchange). Think of a port number as a telephone number, and a computer/server as a telephone exchange. This is often referred to as the Reserved Port Range, since the use of any port in this range is typically reserved for some predefined purpose, and should not typically be used for a general purpose application to avoid conflicts. Generally, these long established and "well known" ports are in the numeric range between. There are many other " well known" ports used for a variety of purposes from FTP to network management, timekeeping and other purposes. There are a finite number of ports that can be assigned on a single machine.Ĭertain port numbers have special meaning, such as the HTTP port number 80, which is used when you browse to a website. Typically this involves a network port on the client and another on the server that the client is communicating with. Any application or service that communicates over a network uses some sort of "port" object as a reference to a specific network connection endpoint.
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