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This is a list of TCP and UDP port numbers used by protocols for operation of network applications. The Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) only need one port for bidirectional traffic. TCP usually uses port numbers that match the services of the corresponding UDP implementations, if they exist, and vice versa.
Similar utilities such as nmap allow a range of ports to be scanned, however they do not allow you to repetitively scan the same ports. Paping operates by attempting to connect to an Internet Protocol TCP/IP port on the target. In the process it measures the time taken for a connection to be established and records any connection failures.
On Linux this program is mostly obsolete, although still included in many distributions. On Linux, netstat (part of "net-tools") is superseded by ss (part of iproute2 ). The replacement for netstat -r is ip route , the replacement for netstat -i is ip -s link , and the replacement for netstat -g is ip maddr , all of which are recommended instead.
netcat (often abbreviated to nc) is a computer networking utility for reading from and writing to network connections using TCP or UDP.The command is designed to be a dependable back-end that can be used directly or easily driven by other programs and scripts.
Nmap features include: Fast scan (nmap -F [target]) – Performing a basic port scan for fast result.Host discovery – Identifying hosts on a network. For example, listing the hosts that respond to TCP and/or ICMP requests or have a particular port open.
Some examples include: FTP (20 and 21), SSH (22), TELNET (23), SMTP (25), HTTP over SSL/TLS (443), and HTTP (80). [e] Registered ports are typically used by end-user applications as ephemeral source ports when contacting servers, but they can also identify named services that have been registered by a third party. Dynamic or private ports can ...
Most UDP port scanners use this scanning method, and use the absence of a response to infer that a port is open. However, if a port is blocked by a firewall, this method will falsely report that the port is open. If the port unreachable message is blocked, all ports will appear open. This method is also affected by ICMP rate limiting. [4]
In computer networking, a port or port number is a number assigned to uniquely identify a connection endpoint and to direct data to a specific service. At the software level, within an operating system, a port is a logical construct that identifies a specific process or a type of network service.