There is a total of 65535 port numbers out of which some are used by the operating system and some are reserved for specific purposes. Let’s learn about some common ports:
- 20-21– These port numbers are used by FTP(File transfer protocol). This protocol is used to exchange files to and from the server.
- 22– This port number is used by SSH(Secure Shell). The communication using this protocol is encrypted and hence it is the secure channel for communication.
- 23– This port number is used by telnet which is used to access virtual machine on a remote place through a text-based communication channel.
- 25, 587– These port numbers are used by Simple Mail Transfer Protocol(SMTP) which is the simplest protocol to send emails from your system.
- 42, 1522– These port numbers are used by WINS(Windows Internet Naming service). It’s work is same as that of DNS, but it’s use is totally different from that of DNS. WINS server is used on a network to map the NetBIOS name( Adapter names) to their respective IP addresses so that NetBIOS applications can communicate over TCP/IP on a network.
- 43– This port number is used by the WHOIS service which are used by client applications to query the server for a particular record.
- 49– This port number is by Terminal Access Controller Access Control system(TACACS). The client running this protocol will forward user credentials to a remote authentication server which will decides to login or not.
- 53– This port number is used by DNS to query recursive or non recursive resolvers for destination IP address.
- 57-68– These ports are used by either DHCP(Dynamic Host Configuration Protocol) or BOOTP(Bootstrap Protocol). Both of these protocols are used to allocate IP address to a host on the network, but the basic difference between both of them is that BOOTP needs machine’s MAC address to provide it with a IP address while DHCP allocates IP address on leased terms as per demands and it is tracked by the DHCP server.
- 69– This port number is used by TFTP(Trivial File transfer protocol) which is used to exchange files between client and server. It is less secure than FTP and it does not let us update file on the server.
- 70– This port number is used by Gopher protocol which is predecessor to world wide web that allows a user to search, distribute and retrieve documents through IP networks.
- 79– This port number is used by Finger/name protocol which is used to search information about other users on a network.
- 80– This port number is used by HTTP(Hyper Text Transfer protocol) which is an application layer protocol use to access world wide web(www) through IP networks.
- 88, 464- These port numbers are used by Kerberos protocol which is an authentication protocol that allows two system communicating over a non-secure network to get authenticated to each other with the help of secret-key cryptography.
- 102- This port number is used by MS Exchange server to communicate with its client.
- 110- This port number is used by Post Office Protocol 3(POP3). This protocol is used to see email messages by downloading them from mail server.
- 113- This port number is used by Ident protocol also known as Identification protocol in which the client sends the TCP port pairs and server replies with the character string from which it identifies the owner of that connection on the server.
- 119– This port number is used by Network News Transfer Protocol(NNTP) which is used for distribution, retrieval and posting of Net news articles. This protocol allows the readers to retrieve the news articles from the server.
- 123– This port number is used by the Network Time Protocol(NTP) which is used to retrieve and sync time from the servers
- 135, 1025- This port number is used by Microsoft RPC(Remote Procedure Call) which is used to call a program on another system that may or may not be on same network.
- 137-139- These port numbers are used by NetBIOS on a system to allow NetBIOS application communicate with each other on a network. Today, NetBIOS communicates over TCP/IP or NBT to satisfy the modern network demands.
- 143– This protocol is used by IMAP4(Internet Message Application Protocol) on the IMAP server to serve its clients so that they can retrieve messages from the server.
- 177- This protocol is used by the XDMCP (X Display Management Control Protocol) which is remote host control protocol. Using this, a host can have a graphical login to the remote host on his system.
- 179– This protocol is used by BGP(Border Gateway Protocol) which is used by systems to exchange their routing information on the Internet or between different domains of internet .
- 318- This protocol is used by the Timestamp Protocol which is used as an authentication protocol for certifying timestamps on documents so that there is an authenticated reason to trust on the document.
- 389- This protocol is used by LDAP(Light Weight Directory Access Protocol) which is used to access directory on the server over the TCP/IP connection.
- 411-412- These port numbers are used by Direct connect protocol which is peer to peer protocol which allows them to connect to each other through hub and share files with each other.
- 443- This port number is used by encrypted Application layer protcol HTTPS or HTTP over SSL. Its function same as that of HTTP rather it provides an encrypted channel for communication.
- 445- This port number is used Server Message Block(SMB) which is a networking protocol used to share files on a network.
- 465- This port number is used by SMTP protocol over SSL to create a secure channel to send mails securely. It functions same as that of SMTP but the SMTP connection via this port is encrypted.
- 500- This port number is used by ISAKMP(Internet Security Association Key Management Protocol) which is used to define standards for peer to peer authentication.
- 512- This port number is used by rexec utility to execute commands on a remote host.
- 513– This port number is used by rlogin (a Unix utility) to remotely login into a system.
- 520- This port number is used by Routing Information Protocol(RIP) which is an IGP (Interior Gateway Protocol) used by routers to share information about routing to find the best find between the source and the destination that has the less hop count.
- 540- This port number is used by UUCP(Unix to Unix Copy Protocol) which is a suite of programs that allows share of files and execution of commands on Unix systems.
- 554- This port number is used by Real Time Streaming Protocol(RTSP). As the protocol itself contains the word streaming, this protocol is used for media streaming used in entertainment and connecting purposes.
- 546-547– These port numbers are used by Dynamic Host Configuration Protocol v6 to configure IPv6 IP address on the host. The DHCPv6 server listens the connection on 547 and client connects to the DHCPv6 server with 546 port number.
- 563- This port number is used by the encrypted version of NNTP protocol. This protocol establishes an encrypted channel of communication with the NNTP server and that’s why it is known as NNTP over SSL.
- 593- This port number is used by Microsoft DCOM (Distributed Component Object Model) that enables softwares use Remote Procedure Calls(RPC) to communicate with each other.
- 636- This port number is used by encrypted version of the LDAP protocol to make a secure channel for clients to communicate with the server. Thus, the protocol running at this port is LDAP over SSL.
- 873- This port number is used by the rsync utility which allows clients to sync files on a remote computer in a network.
- 989-990- This port number is used by the encrypted version of FTP to securely transfer across file across the client and server. This protocol thus also known as the FTP over SSL.
- 993- This port number is used by the encrypted version of IMAP4 protocol so that the email clients can easily retrieve, delete or sync mesaages from the server. Thus this protocol names as IMAP4 over SSL
- 995- This port number is used by the encrypted version of POP3 protocol so that email clients can securely download their messages from the server. Thus this protocol is known as POP3 over SSL.
- 1080- This port number is used by the SOCKS Proxy server which is used to bypass firewall or Internet restrictions on a network. SOCKS means Socket secure and this protocol is implemented at Layer 5 of the OSI model and that’s why it is better than HTTP proxy.
- 1723- This port number is used by MS PPTP (point to point tunneling protocol) which is used in VPN technologies.
- 2049- This port number is used by NFS(Network File System) to allows clients to access files on a computer network.
- 3124, 3127, 8080– These port numbers are used by the proxy at HTTP level to forward packets from the clients and deliver it to the server on the internet.
- 5000- This port number is used by UPnP(Universal Plug n Play) protocol to allow devices like computer, printer and other network devices discover each other’s presence on the internet.