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Port 1687 (nsjtp-ctrl)

IANA assigns port 1687 to nsjtp-ctrl.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
nsjtp-ctrl TCP nsjtp-ctrl - -
nsjtp-ctrl UDP nsjtp-ctrl - -

Check what is listening on port 1687

Linux: is anything listening on TCP 1687?
sudo ss -tlnp 'sport = :1687'
Linux: UDP 1687
sudo ss -ulnp 'sport = :1687'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1687
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1687 '
Windows (Command Prompt)
netstat -ano | findstr :1687
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1687 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1687
From Windows
Test-NetConnection HOST -Port 1687
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1687

Block port 1687 in the firewall

ufw
sudo ufw deny 1687/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1687 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1687 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1687' -Direction Inbound -Protocol TCP -LocalPort 1687 -Action Block
ufw
sudo ufw deny 1687/udp
iptables
sudo iptables -A INPUT -p udp --dport 1687 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1687 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1687' -Direction Inbound -Protocol UDP -LocalPort 1687 -Action Block

Related ports

1685n2nremote1686cvmon1688nsjtp-data1689firefox

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