How do I kill the process using port 53?

On macOS & Linux, run: "sudo systemctl restart systemd-resolved". On Windows PowerShell (as Admin), run: "Stop-Service Dnscache -Force".

Why am I getting "port 53 already in use" (EADDRINUSE)?

This occurs when another background instance of named, dnsmasq, systemd-resolved or a zombie process is already bound to port 53. Use the kill commands above to free the port immediately.

Networking

Risk: High

Port 53 — DNS (Domain Name System)

Q: Is Port 53 safe to expose to the public internet?

Risk level is High. Open DNS resolvers can be weaponized in massive Distributed Denial of Service (DDoS) DNS amplification attacks. Never leave recursive DNS open to the general internet.

Port 53 handles Domain Name System queries, translating human-readable hostnames (e.g. google.com) into numeric IP addresses (e.g. 142.250.190.46). UDP is used for standard queries; TCP is used for large zone transfers.

PORT NUMBER

PROTOCOL

TCP/UDP

DEFAULT PROCESS

named, dnsmasq, systemd-resolved

FIREWALL TARGET

53/tcp/udp

Instant Terminal Fixes for Port 53

macOS & Linux Terminal

1. Check who is listening on port 53:

dig @localhost google.com || sudo ss -ulpn | grep :53

2. Kill process occupying port 53 (EADDRINUSE fix):

sudo systemctl restart systemd-resolved

3. UFW Firewall Allow rule:

sudo ufw allow 53

Windows PowerShell (Admin)

1. Check listening port:

Get-NetTCPConnection -LocalPort 53

2. Force kill process on port 53:

Stop-Service Dnscache -Force

3. Docker Port Forwarding Mapping:

docker run -p 53:53/udp -p 53:53/tcp -d pihole/pihole

Common Error Encountered

listen udp 0.0.0.0:53: bind: address already in use (frequently Ubuntu systemd-resolved)

Security Advisory & Hardening

Open DNS resolvers can be weaponized in massive Distributed Denial of Service (DDoS) DNS amplification attacks. Never leave recursive DNS open to the general internet.

Frequently Asked Questions

Port 53 Questions & Answers

Common questions regarding default services, kill commands, and firewall configurations.

Port 53 is commonly used for DNS (Domain Name System). Port 53 handles Domain Name System queries, translating human-readable hostnames (e.g. google.com) into numeric IP addresses (e.g. 142.250.190.46). UDP is used for standard queries; TCP is used for large zone transfers.

Explore Other Developer Ports

View All Ports Directory

Port 3000React Port 8080HTTP Alternate Port 5173Vite Dev Server (Vue, Svelte, React)Port 80HTTP (Hypertext Transfer Protocol)Port 443HTTPS (HTTP over TLS Port 5000Flask