Port 5445 SMBDIRECT
Port 5445 is the IANA-assigned smbdirect port for Server Message Block over Remote Direct Memory Access (TCP / SCTP).
What is port 5445 used for?
Port 5445 is assigned to smbdirect and uses TCP / SCTP. The IANA registry describes the service as “Server Message Block over Remote Direct Memory Access”. 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.
Ports are the transport-layer address a service listens on. A client that wants to reach smbdirect connects to port 5445. If nothing is listening, the connection is refused. That is why a port conflict appears whenever two processes try to bind the same number.
Use the commands below to confirm whether port 5445 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 Windows networking ports
Source: IANA Service Name and Transport Protocol Port Number Registry. Registered assignee: [Microsoft_Corporation_2].
Check and block port 5445
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 = :5445'
sudo ss -Slpn 'sport = :5445'Check on Windows
Get-NetTCPConnection -LocalPort 5445 -State Listen -ErrorAction SilentlyContinueBlock with UFW
sudo ufw deny 5445/tcpBlock with iptables
sudo iptables -A INPUT -p tcp --dport 5445 -j DROP
sudo iptables -A INPUT -p sctp --dport 5445 -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. UFW and the built-in Windows cmdlets cover TCP and UDP only; this port also lists SCTP, so use nftables, iptables or the vendor's diagnostic tool for those protocols. SCTP and DCCP handling also depends on kernel support, including their diagnostic modules, so a missing result may mean the module is not loaded rather than that nothing is listening.
Is port 5445 safe to expose?
This port is not on our curated list of services with a widely exploited profile. Exposure is only safe when the listening service is intended, patched and protected by a firewall. Keep the listening service patched and remove it if unused. A default-deny firewall policy with explicit allow rules is still the safest baseline.
Where port 5445 is usually used
Most traffic on port 5445 falls into these scenarios. The demo below is a safe way to confirm the listener before you change anything.
- Windows file sharing, printing and domain services inside a LAN.
- Admin tools enumerating shares, printers or RPC endpoints.
- Incident response checking whether lateral-movement ports are reachable.
Enumerate shares
Run this only from a trusted management host; SMB should never be reachable directly from the internet.
smbclient -L //fileserver -p 5445 -NCommon problems with port 5445
Connection refused or timed out
Refused usually means the host is reachable but nothing is listening on port 5445. 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 = :5445' or sudo lsof -i :5445. 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 5445 at a glance
| Port number | 5445 |
|---|---|
| Service name | smbdirect |
| Transport protocol | TCP / SCTP |
| Category | Windows networking |
| Range | Registered port (1024–10000) |
| Risk level | Standard/Low |
| Registered assignee | [Microsoft_Corporation_2] |
| Registry description | Server Message Block over Remote Direct Memory Access |
| Source | IANA Service Name and Transport Protocol Port Number Registry |
Frequently asked questions
What is port 5445 used for?
Port 5445 (SMBDIRECT) uses TCP / SCTP. Server Message Block over Remote Direct Memory Access.
How do I check if port 5445 is open?
On Linux run `sudo ss -tlpn 'sport = :5445'` and `sudo ss -Slpn 'sport = :5445'`. On Windows run `Get-NetTCPConnection -LocalPort 5445 -State Listen -ErrorAction SilentlyContinue` in PowerShell. If the port is open, the output shows a process listening on port 5445; empty output usually means nothing is bound to it. UFW and the built-in Windows cmdlets cover TCP and UDP only; SCTP needs nftables, iptables or the vendor's diagnostic tool.
How do I block port 5445?
With UFW run `sudo ufw deny 5445/tcp`. With iptables run `sudo iptables -A INPUT -p tcp --dport 5445 -j DROP` and `sudo iptables -A INPUT -p sctp --dport 5445 -j DROP`. Persist the iptables rules with your distribution's netfilter-persistent or iptables-save tooling so they survive a reboot. UFW covers TCP and UDP only; use iptables or nftables for SCTP.
Is port 5445 safe to expose?
This port is not on our curated list of services with a widely exploited profile. Exposure is only safe when the listening service is intended, patched and protected by a firewall. Nevertheless, keep the listening service patched and remove it if unused. A default-deny firewall policy with explicit allow rules is still the safest baseline.
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Primary data: IANA Service Name and Transport Protocol Port Number Registry.
Last reviewed 2026-10-30 · Methodology · About · Privacy