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Port 9875 (sapv1)

IANA assigns port 9875 to sapv1: Session Announcement v1.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
sapv1 TCP Session Announcement v1 - RFC 2974
sapv1 UDP Session Announcement v1 - RFC 2974

Check what is listening on port 9875

Linux: is anything listening on TCP 9875?
sudo ss -tlnp 'sport = :9875'
Linux: UDP 9875
sudo ss -ulnp 'sport = :9875'
Linux / macOS: which process owns the port
sudo lsof -nP -i :9875
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':9875 '
Windows (Command Prompt)
netstat -ano | findstr :9875
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 9875 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 9875
From Windows
Test-NetConnection HOST -Port 9875
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 9875

Block port 9875 in the firewall

ufw
sudo ufw deny 9875/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 9875 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 9875 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 9875' -Direction Inbound -Protocol TCP -LocalPort 9875 -Action Block
ufw
sudo ufw deny 9875/udp
iptables
sudo iptables -A INPUT -p udp --dport 9875 -j DROP
nftables
sudo nft add rule inet filter input udp dport 9875 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 9875' -Direction Inbound -Protocol UDP -LocalPort 9875 -Action Block

Related ports

9801sstp-29802davsrcs9876sd9877x510

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