Reference category
Networking
A port number names a service on a host; it does not prove which program is listening. Well-known ports (0–1023) are assigned by IANA, registered ports (1024–49151) are used by common software, and the ephemeral range (49152–65535) is chosen by clients. Knowing the expected owner of a port is the first step in reading a connection error, a firewall rule or a scan result.
The entries below state the default service, the transport protocol and the usual security caveat for each port. When a connection is refused, check for a listener on the expected port before changing anything else; when a port is unexpectedly open, confirm the process and the firewall rule that allow it.
Reference sets in this category (1)
All 21 entries
Network Port Reference 21 entries
20 — FTP dataPort 20 carries FTP data in active mode, from server to client.
21 — FTP controlPort 21 carries FTP commands and responses, including credentials in plain FTP.
22 — SSHPort 22 carries SSH: encrypted remote shell, SFTP, SCP and port forwarding.
23 — TelnetPort 23 is the legacy Telnet service, which sends everything including passwords in clear text.
25 — SMTPPort 25 is the classic SMTP port for server-to-server mail delivery.
53 — DNSPort 53 resolves domain names, over UDP for queries and TCP for large answers or zone transfers.
80 — HTTPPort 80 is the default port for plain HTTP.
110 — POP3Port 110 is the POP3 mailbox protocol, traditionally download-and-delete.
143 — IMAPPort 143 is IMAP, which keeps mail on the server and synchronises folders across devices.
443 — HTTPSPort 443 is the default port for HTTPS and for HTTP/3 over QUIC.
445 — SMBPort 445 carries SMB file sharing on Windows networks and must never face the internet.
587 — SMTP submissionPort 587 is the authenticated submission port for sending mail from a client.
993 — IMAPSPort 993 is IMAP over TLS, encrypted from the first byte.
995 — POP3SPort 995 is POP3 over TLS, encrypted from the first byte.
3306 — MySQLPort 3306 is the default MySQL and MariaDB listener.
3389 — RDPPort 3389 is Microsoft Remote Desktop, a frequent target for brute force and ransomware.
5432 — PostgreSQLPort 5432 is the default PostgreSQL listener.
6379 — RedisPort 6379 is the default Redis listener, and an unauthenticated Redis is a common breach.
8080 — HTTP alternatePort 8080 is a common alternate HTTP port for proxies, development servers and admin panels.
8443 — HTTPS alternatePort 8443 is a common alternate HTTPS port for admin interfaces and application servers.
27017 — MongoDBPort 27017 is the default MongoDB listener and a repeated target of mass ransom campaigns.