Registered · Cross-platform

6881 BitTorrent

TCP Unofficial
UDP Unofficial
SCTP
DCCP

What it is

BitTorrent peer transfer (6881–6889 range).

When / why

P2P file sharing. Frequently blocked on corporate networks.

Protocol status detail

TransportStatusMeaning
TCP Unofficial Not assigned by IANA, but standardized, specified, or widely used on this port.
UDP Unofficial Not assigned by IANA, but standardized, specified, or widely used on this port.
SCTP Not applicable for this transport.
DCCP Not applicable for this transport.

Port range

Registered (1024–49151). Assigned by IANA on request; usable without elevated privileges on most systems.

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Firewall rules for port 6881

Copy-ready inbound rules for the active transports. Replace every <source> placeholder with the specific host, subnet, or CIDR that should reach this port.

ufw

sudo ufw allow proto tcp from <source> to any port 6881

Allow TCP 6881 (BitTorrent). Replace <source> with the network/host that should reach it.

sudo ufw allow proto udp from <source> to any port 6881

Allow UDP 6881 (BitTorrent). Replace <source> with the network/host that should reach it.

firewalld

sudo firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="<source>" port port="6881" protocol="tcp" accept'

Allow TCP 6881 (BitTorrent) from <source>. Run 'firewall-cmd --reload' afterwards.

sudo firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="<source>" port port="6881" protocol="udp" accept'

Allow UDP 6881 (BitTorrent) from <source>. Run 'firewall-cmd --reload' afterwards.

nftables

nft add rule inet filter input ip saddr <source> tcp dport 6881 accept

Allow TCP 6881 (BitTorrent). Assumes table 'inet filter' with an 'input' chain.

nft add rule inet filter input ip saddr <source> udp dport 6881 accept

Allow UDP 6881 (BitTorrent). Assumes table 'inet filter' with an 'input' chain.

iptables

sudo iptables -A INPUT -p tcp -s <source> --dport 6881 -j ACCEPT

Allow TCP 6881 (BitTorrent). Persist with iptables-save/netfilter-persistent.

sudo iptables -A INPUT -p udp -s <source> --dport 6881 -j ACCEPT

Allow UDP 6881 (BitTorrent). Persist with iptables-save/netfilter-persistent.

Azure NSG

az network nsg rule create -g <resource-group> --nsg-name <nsg> -n Allow-bittorrent-6881 --priority 1000 --access Allow --direction Inbound --protocol "*" --source-address-prefixes <source> --destination-port-ranges 6881

Inbound rule for 6881 (BitTorrent). Set <source> to a CIDR; lower priority number = higher precedence.

AWS Security Group

aws ec2 authorize-security-group-ingress --group-id <sg-id> --ip-permissions IpProtocol=tcp,FromPort=6881,ToPort=6881,IpRanges="[{CidrIp=<source-cidr>}]"

Inbound TCP 6881 (BitTorrent). Replace <source-cidr> (e.g. 10.0.0.0/16).

aws ec2 authorize-security-group-ingress --group-id <sg-id> --ip-permissions IpProtocol=udp,FromPort=6881,ToPort=6881,IpRanges="[{CidrIp=<source-cidr>}]"

Inbound UDP 6881 (BitTorrent). Replace <source-cidr> (e.g. 10.0.0.0/16).

GCP firewall

gcloud compute firewall-rules create allow-bittorrent-6881 --direction=INGRESS --action=ALLOW --rules=tcp:6881,udp:6881 --source-ranges=<source-cidr> --network=<network>

Ingress rule for 6881 (BitTorrent). Scope with --source-ranges and optionally --target-tags.

Windows netsh

netsh advfirewall firewall add rule name="Allow BitTorrent 6881/TCP" dir=in action=allow protocol=TCP localport=6881 remoteip=<source>

Inbound TCP 6881 (BitTorrent). Set remoteip to a host/subnet; 'any' is discouraged.

netsh advfirewall firewall add rule name="Allow BitTorrent 6881/UDP" dir=in action=allow protocol=UDP localport=6881 remoteip=<source>

Inbound UDP 6881 (BitTorrent). Set remoteip to a host/subnet; 'any' is discouraged.

Windows PowerShell

New-NetFirewallRule -DisplayName "Allow BitTorrent 6881/TCP" -Direction Inbound -Action Allow -Protocol TCP -LocalPort 6881 -RemoteAddress <source>

Inbound TCP 6881 (BitTorrent). Replace <source> with a host or subnet.

New-NetFirewallRule -DisplayName "Allow BitTorrent 6881/UDP" -Direction Inbound -Action Allow -Protocol UDP -LocalPort 6881 -RemoteAddress <source>

Inbound UDP 6881 (BitTorrent). Replace <source> with a host or subnet.

Rules are generated only for transports marked active for this port. They default to an inbound allow with an explicit source placeholder — never any. Review direction, scope, and rule precedence before applying in production.