Port Number 3 is registered for the Compression Process by the IANA, sometimes also used by the Midnight Commander application
Known Vulnerabilties :
|tcp / udp||trojan||SynDrop|
Reserved Ports : 0 through 1023 (1024 Ports)
Registered Ports : 1024 through 49151
Dynamic or Private Ports : 49152 through 65535
TCP stands for Transmission Control Protocol. TCP is mainly used Protocol in Internet or in any other networks. It is most commonly known as TCP/IP. The IP here stands for Internet Protocol, which deals only with packets. TCP helps in establishing connection between hosts.
UDP stands for User Datagram Protocol. The UDP also uses the IP protocol to establish the connection. But the main difference between the TCP and the UDP is the the data reliability. UDP is used in services that require the loss of packet to a minimum like video streaming. But the UDP is connectionless and does not guarantee any reliable connection.
source : speedguide.net