Port 8888 JUPYTER
Port 8888 is most commonly used by Jupyter. The IANA registry lists TCP / UDP for this number.
What is port 8888 used for?
Port 8888 is most commonly used by Jupyter. Jupyter Notebook and many development proxies commonly listen on port 8888. It sits in the registered range, the block used by databases, application servers and developer tooling. Port conflicts here are common when several local services start at once. The same port is also registered under ddi-udp-1.
Each transport reaches a different service on this number, so match the protocol to the service you are diagnosing. A TCP check says nothing about a UDP listener on the same port, and the reverse is also true. Both transports still bind to the same number, which is why two processes can collide even when they use different protocols.
Use the commands below to confirm whether port 8888 is actually in use before you change firewall rules. Blocking the port stops new inbound traffic at the firewall, but it does not stop a local process from listening, and it does not remove the service from the machine.
Browse all Development servers ports
Source: IANA Service Name and Transport Protocol Port Number Registry. Registered assignee: [Fred_Yao].
Check and block port 8888
Copy-ready commands for the protocols assigned to this port. Run the check first, then block only what should not be reachable.
Check on Linux
sudo ss -tlpn 'sport = :8888'
sudo ss -ulpn 'sport = :8888'Check on Windows
Get-NetTCPConnection -LocalPort 8888 -State Listen -ErrorAction SilentlyContinue
Get-NetUDPEndpoint -LocalPort 8888 -ErrorAction SilentlyContinueBlock with UFW
sudo ufw deny 8888/tcp
sudo ufw deny 8888/udpBlock with iptables
sudo iptables -A INPUT -p tcp --dport 8888 -j DROP
sudo iptables -A INPUT -p udp --dport 8888 -j DROPThese commands are examples for a typical host. Check the listener before you change firewall rules, and persist iptables rules with iptables-save or netfilter-persistent. On Windows, use Windows Defender Firewall or New-NetFirewallRule for persistent blocks. The iptables rules here cover IPv4; mirror them with ip6tables if IPv6 is enabled.
Is port 8888 safe to expose?
Jupyter Notebook and similar development consoles can execute arbitrary code and often lack authentication. Never expose them to the public internet. Treat this port as sensitive. Restrict it to trusted networks or a VPN, require authentication and logging, and never expose it directly to the public internet without a hardened gateway in front.
Where port 8888 is usually used
Most traffic on port 8888 falls into these scenarios. The demo below is a safe way to confirm the listener before you change anything.
- Starting a framework development server and opening the localhost URL it prints.
- Testing a frontend against a local API, proxy or mock service.
- Hot-reload sessions that should stay bound to 127.0.0.1 instead of a public interface.
Start Jupyter
Jupyter prints a tokenised localhost URL when it starts; do not expose that URL publicly.
jupyter notebook --port 8888Common problems with port 8888
Connection refused or timed out
Refused usually means the host is reachable but nothing is listening on port 8888. A timeout more often means a firewall drop, a wrong host or a service bound to a different interface.
Port already in use
Find the process holding the port with sudo ss -tlpn 'sport = :8888' or sudo lsof -i :8888. Stop that process or configure it to bind another port; killing it without identifying it can take down a production service.
Firewall rule did not survive a reboot
UFW and Windows Firewall keep rules across restarts. Raw iptables rules do not: save them with iptables-save or the netfilter-persistent package, and re-apply after upgrades that reset the ruleset.
The port is blocked but still reachable
A firewall rule filters inbound traffic; it does not close the listener. Confirm with the check command above and bind the service to 127.0.0.1 when only local clients need it.
Port 8888 at a glance
| Port number | 8888 |
|---|---|
| IANA service name | ddi-tcp-1 |
| Commonly used by | Jupyter |
| Aliases | ddi-udp-1 |
| Transport protocol | TCP / UDP |
| Assignments by protocol |
|
| Category | Development servers |
| Range | Registered port (1024–10000) |
| Risk level | High |
| Registered assignee | [Fred_Yao] |
| Registry description | NewsEDGE server TCP (TCP 1) |
| Source | IANA Service Name and Transport Protocol Port Number Registry |
Frequently asked questions
What is port 8888 used for?
Port 8888 (JUPYTER). The IANA registry assigns a different service on each transport protocol: TCP ddi-tcp-1; UDP ddi-udp-1. Jupyter Notebook and many development proxies commonly listen on port 8888.
How do I check if port 8888 is open?
On Linux run `sudo ss -tlpn 'sport = :8888'` and `sudo ss -ulpn 'sport = :8888'`. On Windows run `Get-NetTCPConnection -LocalPort 8888 -State Listen -ErrorAction SilentlyContinue` and `Get-NetUDPEndpoint -LocalPort 8888 -ErrorAction SilentlyContinue` in PowerShell. If the port is open, the output shows a process listening on port 8888; empty output usually means nothing is bound to it.
How do I block port 8888?
With UFW run `sudo ufw deny 8888/tcp` and `sudo ufw deny 8888/udp`. With iptables run `sudo iptables -A INPUT -p tcp --dport 8888 -j DROP` and `sudo iptables -A INPUT -p udp --dport 8888 -j DROP`. Persist the iptables rules with your distribution's netfilter-persistent or iptables-save tooling so they survive a reboot.
Is port 8888 safe to expose?
Jupyter Notebook and similar development consoles can execute arbitrary code and often lack authentication. Never expose them to the public internet. Nevertheless, treat this port as sensitive. Restrict it to trusted networks or a VPN, require authentication and logging, and never expose it directly to the public internet without a hardened gateway in front.
Related ports
Primary data: IANA Service Name and Transport Protocol Port Number Registry.
Last reviewed 2026-10-30 · Methodology · About · Privacy