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Port 199 (smux)

IANA assigns port 199 to smux: SMUX.

Well-known (system) port, 0-1023 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
smux TCP SMUX Marshall Rose -
smux UDP SMUX Marshall Rose -

Check what is listening on port 199

Linux: is anything listening on TCP 199?
sudo ss -tlnp 'sport = :199'
Linux: UDP 199
sudo ss -ulnp 'sport = :199'
Linux / macOS: which process owns the port
sudo lsof -nP -i :199
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':199 '
Windows (Command Prompt)
netstat -ano | findstr :199
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 199 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 199
From Windows
Test-NetConnection HOST -Port 199
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 199

Block port 199 in the firewall

ufw
sudo ufw deny 199/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 199 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 199 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 199' -Direction Inbound -Protocol TCP -LocalPort 199 -Action Block
ufw
sudo ufw deny 199/udp
iptables
sudo iptables -A INPUT -p udp --dport 199 -j DROP
nftables
sudo nft add rule inet filter input udp dport 199 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 199' -Direction Inbound -Protocol UDP -LocalPort 199 -Action Block

Related ports

197dls198dls-mon200src201at-rtmp

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.