To configure firewall as a system admin or even as a normal computer user we need to know the port numbers which will remain open. Here is a list of common port numbers of some common services.

File Transfer Protocol (FTP): 21 Secure File Transfer Protocol (sFTP): 22 File Transfer Protocol (FTPS): 990 Trivial File Transfer Protocol (TFTP): 69

Remote Login Protocol (SSH): 22 Telnet: 23 Telnet over TLS/SSL: 992 Gopher: 70 Network News Transfer Protocol (NNTP): 119

World Wide Web / HTTP (WWW/HTTP): 80 or 8080 World Wide Web / HTTP over TLS/SSL (HTTPs): 443

Simple Mail Transfer Protocol (SMTP): 25 Post Office Protocol v2 (POP2): 109 Post Office Protocol v3 (POP3): 110 Post Office Protocol v3 over TLS/SSL (SPOP3/POP3S): 995 Internet Message Access Protocol v3 (IMAP3): 220 Internet Message Access Protocol v4 (IMAP4): 143 Internet Message Access Protocol v4 with TLS/SSL (IMAP4): 585 or 993

Internet Relay Chat Protocol (IRC): 194 Internet Relay Chat Protocol over TLS/SSL (IRCS): 994 Printer Spooler: 515