Well-known · Linux/Unix

513 rlogin / who

TCP Yes
UDP Yes
SCTP —
DCCP —

What it is

Remote login (TCP); rwho service (UDP).

When / why

Insecure r-command — replace with SSH.

Protocol status detail

TransportStatusMeaning
TCP Yes Assigned by IANA and standardized, specified, or widely used on this port.
UDP Yes Assigned by IANA and standardized, specified, or widely used on this port.
SCTP — Not applicable for this transport.
DCCP — Not applicable for this transport.
« 512 rexec / comsat 514 Syslog / RSH »

Port range

Well-known (0–1023). System port for a core service. On Unix-like systems, binding it requires superuser privileges.

Browse all ports →

Firewall rules for port 513

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 513

Allow TCP 513 (rlogin / who). Replace <source> with the network/host that should reach it.

sudo ufw allow proto udp from <source> to any port 513

Allow UDP 513 (rlogin / who). 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="513" protocol="tcp" accept'

Allow TCP 513 (rlogin / who) from <source>. Run 'firewall-cmd --reload' afterwards.

sudo firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="<source>" port port="513" protocol="udp" accept'

Allow UDP 513 (rlogin / who) from <source>. Run 'firewall-cmd --reload' afterwards.

nftables

nft add rule inet filter input ip saddr <source> tcp dport 513 accept

Allow TCP 513 (rlogin / who). Assumes table 'inet filter' with an 'input' chain.

nft add rule inet filter input ip saddr <source> udp dport 513 accept

Allow UDP 513 (rlogin / who). Assumes table 'inet filter' with an 'input' chain.

iptables

sudo iptables -A INPUT -p tcp -s <source> --dport 513 -j ACCEPT

Allow TCP 513 (rlogin / who). Persist with iptables-save/netfilter-persistent.

sudo iptables -A INPUT -p udp -s <source> --dport 513 -j ACCEPT

Allow UDP 513 (rlogin / who). Persist with iptables-save/netfilter-persistent.

Azure NSG

az network nsg rule create -g <resource-group> --nsg-name <nsg> -n Allow-rloginwho-513 --priority 1000 --access Allow --direction Inbound --protocol "*" --source-address-prefixes <source> --destination-port-ranges 513

Inbound rule for 513 (rlogin / who). 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=513,ToPort=513,IpRanges="[{CidrIp=<source-cidr>}]"

Inbound TCP 513 (rlogin / who). 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=513,ToPort=513,IpRanges="[{CidrIp=<source-cidr>}]"

Inbound UDP 513 (rlogin / who). Replace <source-cidr> (e.g. 10.0.0.0/16).

GCP firewall

gcloud compute firewall-rules create allow-rloginwho-513 --direction=INGRESS --action=ALLOW --rules=tcp:513,udp:513 --source-ranges=<source-cidr> --network=<network>

Ingress rule for 513 (rlogin / who). Scope with --source-ranges and optionally --target-tags.

Windows netsh

netsh advfirewall firewall add rule name="Allow rlogin / who 513/TCP" dir=in action=allow protocol=TCP localport=513 remoteip=<source>

Inbound TCP 513 (rlogin / who). Set remoteip to a host/subnet; 'any' is discouraged.

netsh advfirewall firewall add rule name="Allow rlogin / who 513/UDP" dir=in action=allow protocol=UDP localport=513 remoteip=<source>

Inbound UDP 513 (rlogin / who). Set remoteip to a host/subnet; 'any' is discouraged.

Windows PowerShell

New-NetFirewallRule -DisplayName "Allow rlogin / who 513/TCP" -Direction Inbound -Action Allow -Protocol TCP -LocalPort 513 -RemoteAddress <source>

Inbound TCP 513 (rlogin / who). Replace <source> with a host or subnet.

New-NetFirewallRule -DisplayName "Allow rlogin / who 513/UDP" -Direction Inbound -Action Allow -Protocol UDP -LocalPort 513 -RemoteAddress <source>

Inbound UDP 513 (rlogin / who). 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.