Today I want to describe the most important ports that a developer probably should know about. So check this out:

• 20: ftp-data (file transfer; default data)
• 21: ftp (file transfer; control)
• 22: secure shell
• 23: telnet
• 25: simple mail transfer
• 53: domain name system (DNS)
• 67: boostrap protocol server (dhcp server)
• 68: boostrap protocol client
• 69: tpft (trivial file transfer protocol)
• 80: http
• 110: post office protocol – version 3 (pop 3)
• 119: network news transfer protocol
• 123: network time protocol
• 137/138/139: NetBIOS
• 143: internet message access protocol (imap)
• 161/162: simple network managment
• 443: https
• 445: Microsoft DS
• 465: smpts (smtp secure)
• 500: ip-security vpn
• 587: simple mail transfer submission (smtp)
• 993: impas (imap4 over tls/ssl)
• 995: pop3 over tls/ssl
• 989/990: ftp over tls/ssl
• 3389: remote desktop