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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.
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.
Packet Sender is an open source utility to allow sending and receiving TCP and UDP packets. It also supports TCP connections using SSL, intense traffic generation, HTTP(S) GET/POST requests, and panel generation.
UDP is a simple message-oriented transport layer protocol that is documented in RFC 768. Although UDP provides integrity verification (via checksum ) of the header and payload, [ 4 ] it provides no guarantees to the upper layer protocol for message delivery and the UDP layer retains no state of UDP messages once sent.
Tools commonly used to perform banner grabbing are Telnet, Nmap and Netcat. For example, one could establish a connection to a target web server using Netcat , then send an HTTP request. The response will typically contain information about the service running on the host:
Hole punching (or sometimes punch-through) is a technique in computer networking for establishing a direct connection between two parties in which one or both are behind firewalls or behind routers that use network address translation (NAT).
Another message send service is defined as a datagram-based application on UDP. A service listens for UDP datagrams on port 18. When a datagram is received by the receiver, an answering datagram is sent back to the sender containing exactly the same data.
These messages serve to collect round-trip timing, gather and send data related to congestion control, synchronize repair windows, and make notifications of a sender's status. There is a core set of specified and enumerated NORM_CMD messages, as well as a range other available types for application-specific use.