Introduction

  • The list of port numbers  are specified in RFC 1700.
  • The concept of port numbers was established by the early developers of the ARPANET.
  • The Internet Assigned Numbers Authority (IANA) is responsible for maintaining the official assignments of port numbers for specific uses.

Definition

  • Port/Network/Communication Port
    • In computer networking, a port is a communication endpoint.
    • The ports are used by TCP and UDP to deliver the data to the right application.
    • Ports are typically used to map data to a particular process running on a client.
    • As software, for an operating system, a port is a logical construct that identifies a specific process or a type of network service.
    • network port is a process/application-specific software construct serving as a communication endpoint.
    • Communication port is a medium through which, an application establish a connection with another application by binding a socket by a port number.
    • In computer and telecommunication devices, a port is generally a specific place for being physically connected to some other device. It is usually a socket and plug of some kind. Typically, a personal computer has one or more serial ports and usually one/few parallel port.
  • Port Number
    • When a process starts up, it registers/creates a unique port number with the protocol stack.It is the logical address of each application or process that uses a network or the Internet to communicate. 
    • Every service in a network has unique port number.
    • In Computer Networks, ports are identified for each protocol and IP address as 16-bit unsigned positive integer numbers, commonly known as the port number.
    • It is a way to identify a specific process/application that uses a network or the Internet to communicate via the server.
    • The port number is used to direct the data to the correct location within this device.
    • The port number identifies what type/category of port an application/process is.
    • Port number permits unique identification of several simultaneous processes using
      TCP/UDP
  • Port Address
    • port address is the logical address (in the form of integer number ranging from 0 to 65535) of each application or process that uses a network or the Internet to communicate.

Features

  • A port identifies a specific application running on an machine. A port is identified by port number.
  • The most common protocols that use port numbers are the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) i.e. port numbers are mainly used in TCP and UDP based networks.
  • A port number is always associated with an IP address of a host and the protocol type of the communication.
  • The port numbers are specified by a 16-bit number i.e. the port number is ranges from 0 to 65535(216 = 65536).
  • There are a total of 65,535 TCP Ports and another 65,535 UDP ports.
  • IANA maintains the official list of well-known and registered ports.
  • port number uniquely identifies a network-based application on a computer. Each application/program is allocated a 16-bit integer port number. In other words, the IP address identifies the computer host, and the port number specifies the particular process running on that host.
  • This number is assigned automatically by the OS, manually by the user or is set as a default for some popular applications.
  • Port number works with IP address where IP address is used to identify the destination computer/node in a network, whereas the port number further specifies the destination end of an application/program in that computer.
  • Only one process per protocol can listen/work on a given port i.e., two different processes, one using UDP and another TCP can both listen on unique port number. However, two processes using the same transport protocol cannot listen on the same port number.
  • All outgoing data packets contain application/process port numbers in the packet header to enable the receiver to distinguish the specific application on receiving end.

Types

There are 3 types of port –

(A) Well Known/System/Global/Reserved/Common/Restricted Port : 
    • The port numbers in the range from 0 to 1023 are the well-known ports.
    • These ports are registered & controlled by IANA i.e. these are official ports.
    • They are used by system processes that provide widely-used types of network services i.e. these port numbers are assigned to the server side of an application and are already reserved for specific applications by IANA (Internet Assigned Number Authority).
    • They are reserved for privileged services.
    • For example – 
      • Application/Process Name  –  Port Number(Associated Protocol)
        • FTP  –  20 (For data) & 21(For Control)/TCP
        • TFTP  –  69/UDP
        • Telnet  –  23/TCP
        • SMTP  –  25/TCP
        • DNS – 53/TCP or UDP
        • IMAP  –  143
        • POP3  –  110/TCP
        • Gopher  –  70
        • HTTP  –  80
        • HTTPS  –  443/TCP
        • DHCP  –  As client (546) & As server  (547). 
        • IRC  –  194
        • SNMP  –  161/UDP
        • NFS  –  2049
        • BOOTPS  –  67 (for Server)/UDP
        • BOOTPC – 68 (for Client)/UDP
        • LOGIN  –  513/TCP
        • BGP – 179/TCP
        • TIME – 37/UDP
        • WHOIS –  43/TCP
(B) Registered Ports :
    • These ports are not registered with IANA hence these are unofficial ports.
    • These port numbers have been publicly defined as a convenient service for the Internet community to help them avoid vendor conflicts.
    • The range of port number from 1024 to 49151 are the registered ports.
    • User level process/services generally use port number value >= 1024.
(C) Dynamic/Private/ Ephemeral Port
    • These ports are conflicts i.e. these ports are in use for multiple applications (which may be official or unofficial).
    • These ports are ranges from 49152–65535.
    • It can be used freely by any client or server application.

 290 total views,  1 views today


0 Comments

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.