Port 20: FTP Data
Data channel for active-mode FTP. FTP sends passwords in clear text. Use SFTP (over SSH, port 22) instead.
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Port Lookup
Port 20 at a glance
Port20
ProtocolTCP
ServiceFTP Data
Open to the Internet?Only to addresses that need it
See What Is Listeningss -lntup | grep ':20 '
Test From Outsidenc -zv your-server 20
Block with UFWufw deny 20/tcp
Block with nftablesnft add rule inet filter input tcp dport 20 drop
FTP Data uses TCP port 20. Data channel for active-mode FTP.
FTP sends passwords in clear text. Use SFTP (over SSH, port 22) instead.
Allow port 20 only from the addresses that need it: your office, a VPN or a bastion host. The firewall rule generator builds those rules for nftables, iptables and UFW.
Other Ports
20 FTP Data21 FTP22 SSH23 Telnet25 SMTP53 DNS67 DHCP Server80 HTTP110 POP3123 NTP143 IMAP161 SNMP389 LDAP443 HTTPS445 SMB465 SMTPS514 Syslog587 Mail Submission853 DNS over TLS993 IMAPS995 POP3S1194 OpenVPN1433 Microsoft SQL Server1900 SSDP / UPnP2049 NFS2083 cPanel (SSL)2087 WHM (SSL)3306 MySQL / MariaDB3389 RDP3478 STUN / TURN5060 SIP5432 PostgreSQL5900 VNC6379 Redis8006 Proxmox VE8080 HTTP Alternate8443 HTTPS Alternate11211 Memcached25565 Minecraft27017 MongoDB51820 WireGuard
Questions
What is port 20 used for?
FTP Data. Data channel for active-mode FTP.
Is it safe to open port 20?
Only to addresses that need it. FTP sends passwords in clear text. Use SFTP (over SSH, port 22) instead.
How do I check if port 20 is open?
On the server, ss -lntup | grep ':20 ' shows what is listening. From another machine, nc -zv your-server 20 shows whether the firewall lets it through.
How do I block port 20?
With UFW: ufw deny 20/tcp. With nftables, add a drop rule for dport 20 in your input chain.
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