Some important TCP port numbers

Description TCP Port Number
POP3 110
SMTP 25
IMAP 143
HTTP 80
HTTPS 443
TELNET 23
FTP (For Data Transfer) 20
FTP (To establish connection between computers) 21
Secure SMTP (SSMTP) 465
Secure IMAP (IMAP4 SSL) 585
IMAP4 over SSL 993
Secure POP3(SSL-POP) 995
Remote Desktop 3389
DNS (Client/Server) 53
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