What is Ports ?
Port is logical communication endpoints that exist on a computer or server. In other words port is a virtual point where network connections start and end. Ports allow computers to easily differentiate between different kinds of traffic: emails go to a different port than webpages, for instance, even though both reach a computer over the same Internet connection. A port number is a unique identifier used with an IP address. A port is a 16-bit unsigned integer, and the total number of ports available in the TCP/IP model is 65,535 ports. The most common transport protocols that use port numbers are the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).
Inbound Port: A logical communication opening on a server that is listening for a connection from a client.
Outbound Port: A logical communication opening created on a client in order to call out to a server that is listening for a connection.
Ports can be any number between 0 to 65535. Ports between 0 to 1023 are considered as well known ports and are assigned by the Internet Assigned Numbers Authority (IANA). Ports between 1024 to 49,151 are considered registered ports and are usually assigned to proprietary protocols. Ports between 49,152 to 65,535 can be used by any application without being registered with Internet Assigned Numbers Authority (IANA). Any port that is associated with a service or function that is non-essential to the operation of your computer or network is known as unnecessary ports.
What is Protocols ?
In networking, a protocol is a set of rules that determine how data is transmitted between different devices. It allows connected devices to communicate with each other. Network protocols are the reason you can easily communicate with people all over the internet, and thus play a critical role in modern digital communications. Protocols are established by international or industry wide organizations.
The most famous Protocols with port numbers are shown below.
| Port Numbers | Protocols | Description |
| 21 TCP | FTP | File Transfer Protocol is used to transfer files from host to host |
| 22 TCP/UDP | SSH | Secure Shell is used to remotely administer network devices and systems. SCP is used for secure copy and SFTP for secure FTP. |
| 23 TCP/UDP | Telnet | Unencrypted method to remotely administer network devices (should not be used) |
| 25 TCP | SMTP | Simple Mail Transfer Protocol is used to send email over the Internet |
| 53 TCP/UDP | DNS | Domain Name Service is used to resolve hostnames to IPs and IPs to hostnames |
| 69 UDP | TFTP | Trivial FTP is used as a simplified version of FTP to put a file on a remote host, or get a file from a remote host |
| 80 TCP | HTTP | Hyper Text Transfer Protocol is used to transmit web page data to a client for unsecured web browsing. |
| 88 TCP/UDP | Kerberos | Used for network authentication using a system of tickets within a Windows domain |
| 110 TCP | POP3 | Post Office Protocol v3 is used to receive email from a mail server |
| 119 TCP | NNTP | Network News Transfer Protocol is used to transport Usenet articles |
| 123 UDP | NTP | Network Time Protocol (NTP) is used to synchronize the devices on the Internet. Even most modern operating systems support NTP as a basis for keeping an accurate clock. |
| 135 TCP/UDP | PC/DCOM[1]scm | Remote Procedure Call is used to located DCOM ports request a service from a program on another computer on the network |
| 137,138,139 TCP/UDP | NetBIOS | NetBIOS is used to conduct name querying, sending of data, and other functions over a NetBIOS connection |
| 143 TCP | IMAP | Internet Message Access Protocol is used to receive email from a mail server with more features than POP3 |
| 161 UDP | SNMP | Simple Network Management Protocol is used to remotely monitor network devices |
| 162 TCP/UDP | SNMPTRAP | Used to send Trap and Inform Requests to the SNMP Manager on a network |
| 389 TCP/UDP | LDAP | Lightweight Directory Access Protocol is used to maintain directories of users and other objects |
| 443 TCP | HTTPS | Hyper Text Transfer Protocol Secure is used to transmit web page data to a client over an SSL/TLS-encrypted connection |
| 445 TCP | SMB | Server Message Block is used to provide shared access to files and other resources on a network |
| 465/587 TCP | SMTP with SSL/TLS | Simple Mail Transfer Protocol used to send email over the Internet with an SSL and TLS secured connection |
| 514 UDP | Syslog | Syslog is used to conduct computer message logging, especially for routers and firewall logs |
| 636 TCP/UDP | LDAP SSL/TLS | LDAP is used to maintain directories of users and other objects over an encrypted SSL/TLS connection |
| 860 TCP | iSCSI | iSCSI is used for linking data storage facilities over IP |
| 989/990 TCP | FTPS | File Transfer Protocol Secure is used to transfer files from host to host over an encrypted connection |
| 993 TCP | IMAP4 with SSL/TLS | Internet Message Access Protocol is used to receive email from a mail server over an SSL/TLS[1]encrypted connection |
| 995 TCP | POP3 (SSL/TLS) | Post Office Protocol v3 is used to receive email from a mail server using an SSL/TLS-encrypted connection |
| 1433 TCP | Ms-sql-s | Microsoft SQL server is used to receive SQL database queries from clients |
| 1645/1646 UDP | RADIUS (alternative) | Remote Authentication Dial-In User Service is used for authentication and authorization (1645) and accounting (1646) |
| 1701 UDP | L2TP | Layer 2 Tunnel Protocol is used as an underlying VPN protocol but has no inherent security |
| 1723 TCP/UDP | PPTP | Point-to-Point Tunneling Protocol is an underlying VPN protocol with built-in security |
| 1812/1813 UDP | RADIUS | Remote Authentication Dial-In User Service is used for authentication and authorization (1812) and accounting (1813) |
| 3225 TCP/UDP | FCIP | Fibre Channel IP is used to encapsulate Fibre Channel frames within TCP/IP packets |
| 3260 TCP | iSCSI Target | iSCSI Target is as the listening port for iSCSI-targeted devices when linking data storage facilities over IP |
| 3389 TCP/UDP | RDP | Remote Desktop Protocol is used to remotely view and control other Windows systems via a Graphical User Interface |
| 3868 TCP | Diameter | A more advanced AAA protocol that is a replacement for RADIUS |
| 6514 TCP | Syslog over TLS | It is used to conduct computer message logging, especially for routers and firewall logs, over a TLS-encrypted connection |
Thanks for helping me bro, i am confused with the port number of Radius protoco but now its clear.