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Port 9911 (sype-transport)

IANA assigns port 9911 to sype-transport: SYPECom Transport Protocol.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
sype-transport TCP SYPECom Transport Protocol Sylvain Pedneault -
sype-transport UDP SYPECom Transport Protocol Sylvain Pedneault -

Registry dates for this port: registered 2003-03.

Check what is listening on port 9911

Linux: is anything listening on TCP 9911?
sudo ss -tlnp 'sport = :9911'
Linux: UDP 9911
sudo ss -ulnp 'sport = :9911'
Linux / macOS: which process owns the port
sudo lsof -nP -i :9911
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':9911 '
Windows (Command Prompt)
netstat -ano | findstr :9911
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 9911 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 9911
From Windows
Test-NetConnection HOST -Port 9911
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 9911

Block port 9911 in the firewall

ufw
sudo ufw deny 9911/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 9911 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 9911 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 9911' -Direction Inbound -Protocol TCP -LocalPort 9911 -Action Block
ufw
sudo ufw deny 9911/udp
iptables
sudo iptables -A INPUT -p udp --dport 9911 -j DROP
nftables
sudo nft add rule inet filter input udp dport 9911 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 9911' -Direction Inbound -Protocol UDP -LocalPort 9911 -Action Block

Related ports

9903multicast-ping9909domaintime9925xybrid-cloud9950apc-9950

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