- serial ports
- Ethernet , USB & serial
- Physical connections
- Virtual ports are there to get access to data for particular application
- logical connection to exchange data
- Ports can be open , closed
- Ports provide particular service
- From 0 to 1023 – well known ports assigned to common protocols and services
- From 1024 to 49151 – registered ports assigned by ICANN to a specific service
- From 49152 to 65535 – ephemeral ports or (dynamic ,private, high) ports . Can be used by any service on an ad hoc basis. Ports are assigned when a session is established, and released when the session ends.
Common port numbers
| Port number | Service name | Transport Protocol |
|---|---|---|
| 20, 21 | File Transfer Protocol (FTP) | TCP |
| 22 | Secure Shell (SSH) | TCP and UDP |
| 23 | Telnet | TCP |
| 25 | Simple Mail Transfer Protocol (SMTP) | TCP |
| 50, 51 | IPSec (ESP , AH) | |
| 53 | Domain Name System (DNS) | TCP and UDP |
| 67, 68 | Dynamic Host Configuration Protocol (DHCP) | UDP |
| 69 | Trivial File Transfer Protocol (TFTP) | UDP |
| 80 | HyperText Transfer Protocol (HTTP) | TCP |
| 110 | Post Office Protocol (POP3) | TCP |
| 119 | Network News Transport Protocol (NNTP) | TCP |
| 123 | Network Time Protocol (NTP) | UDP |
| 135-139 | NetBIOS | TCP and UDP |
| 143 | Internet Message Access Protocol (IMAP4) | TCP and UDP |
| 161, 162 | Simple Network Management Protocol (SNMP) | TCP and UDP |
| 389 | Lightweight Directory Access Protocol | TCP and UDP |
| 443 | HTTP with Secure Sockets Layer (SSL) | TCP and UDP |
| 989, 990 | FTP over SSL/TLS (implicit mode) | TCP |
| 3389 | Remote Desktop Protocol | TCP and UDP |