Port 443 — HTTPS

TCP well-known

What runs on port 443

Encrypted web traffic. The default for essentially all modern web services, and the transport for HTTP/2 and HTTP/3.

Security considerations

HTTP/3 runs over QUIC on UDP 443 — if you firewall only TCP, HTTP/3 silently fails and clients fall back.

Checking whether something is listening

# Linux / macOS — what is bound to the port
sudo lsof -i :443
sudo ss -lntp | grep :443

# Windows
netstat -ano | findstr :443
Get-NetTCPConnection -LocalPort 443

# is it reachable from outside?
nc -zv example.com 443
curl -v telnet://example.com:443

Freeing the port

# find the process, then stop it
sudo lsof -ti :443 | xargs kill        # Linux / macOS
netstat -ano | findstr :443            # note the PID, then:
taskkill /PID <pid> /F                    # Windows

Other common ports

• Port 20 — FTP data
• Port 21 — FTP control
• Port 22 — SSH / SFTP
• Port 23 — Telnet
• Port 25 — SMTP
• Port 53 — DNS
• Port 67 — DHCP server
• Port 68 — DHCP client
• Port 69 — TFTP
• Port 80 — HTTP
• Port 110 — POP3
• Port 123 — NTP
• Port 143 — IMAP
• Port 161 — SNMP
• Port 389 — LDAP
• Port 445 — SMB
• Port 465 — SMTPS
• Port 514 — Syslog

All port numbers