![]() Now you should be more familiar with ports, but we are still not ready to write our port scanner.įirst, we need to discuss what it means for a port to be open. Ports in the 2nd range are assigned by the IANA (Internet Assigned Numbers Authority).Īnd the 3rd range is used for “dynamic” or “ephemeral” ports, these are the ports used by the client side of the connection to receive data from the server. Ports can be divided into 3 groups: Range There are 65.535 ports available in total, but in practice not all of them are used regularly. Then if there is a listening process the packet is delivered to it. When the OS receives a TCP/IP packet it looks at the destination port & tries to find a process which is listening on this port. (Operating System) level is just a “file descriptor” associated with a process.Ī file descriptor is just a number which is used to reference an open I/O channel, like stdout (standard output), a network socket or a file. When we talk about ports what are we really talking about? A port at the O.S. ![]() Let’s gets started by talking about ports! What Is a Port? It’s also a good exercise to learn more about how Ruby network programming works. Writing a port scanner is a great way to learn the basics of the TCP protocol, which is the transport layer used by most internet protocols (including HTTP & SSH). Why would you want to write a port scanner? ![]()
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February 2023
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