Registered · Cross-platform

5900 VNC / RFB

TCP Yes
UDP Unofficial
SCTP —
DCCP —

What it is

Remote Frame Buffer protocol for VNC remote control.

When / why

Cross-platform remote desktop. Tunnel over SSH/VPN — VNC auth is weak.

Protocol status detail

TransportStatusMeaning
TCP Yes Assigned by IANA and 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.
« 5800 VNC over HTTP 5931 Ammyy Admin »

Port range

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

Browse all ports →

Firewall rules for port 5900

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 5900

Allow TCP 5900 (VNC / RFB). Replace <source> with the network/host that should reach it.

sudo ufw allow proto udp from <source> to any port 5900

Allow UDP 5900 (VNC / RFB). 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="5900" protocol="tcp" accept'

Allow TCP 5900 (VNC / RFB) from <source>. Run 'firewall-cmd --reload' afterwards.

sudo firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="<source>" port port="5900" protocol="udp" accept'

Allow UDP 5900 (VNC / RFB) from <source>. Run 'firewall-cmd --reload' afterwards.

nftables

nft add rule inet filter input ip saddr <source> tcp dport 5900 accept

Allow TCP 5900 (VNC / RFB). Assumes table 'inet filter' with an 'input' chain.

nft add rule inet filter input ip saddr <source> udp dport 5900 accept

Allow UDP 5900 (VNC / RFB). Assumes table 'inet filter' with an 'input' chain.

iptables

sudo iptables -A INPUT -p tcp -s <source> --dport 5900 -j ACCEPT

Allow TCP 5900 (VNC / RFB). Persist with iptables-save/netfilter-persistent.

sudo iptables -A INPUT -p udp -s <source> --dport 5900 -j ACCEPT

Allow UDP 5900 (VNC / RFB). Persist with iptables-save/netfilter-persistent.

Azure NSG

az network nsg rule create -g <resource-group> --nsg-name <nsg> -n Allow-vncrfb-5900 --priority 1000 --access Allow --direction Inbound --protocol "*" --source-address-prefixes <source> --destination-port-ranges 5900

Inbound rule for 5900 (VNC / RFB). 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=5900,ToPort=5900,IpRanges="[{CidrIp=<source-cidr>}]"

Inbound TCP 5900 (VNC / RFB). 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=5900,ToPort=5900,IpRanges="[{CidrIp=<source-cidr>}]"

Inbound UDP 5900 (VNC / RFB). Replace <source-cidr> (e.g. 10.0.0.0/16).

GCP firewall

gcloud compute firewall-rules create allow-vncrfb-5900 --direction=INGRESS --action=ALLOW --rules=tcp:5900,udp:5900 --source-ranges=<source-cidr> --network=<network>

Ingress rule for 5900 (VNC / RFB). Scope with --source-ranges and optionally --target-tags.

Windows netsh

netsh advfirewall firewall add rule name="Allow VNC / RFB 5900/TCP" dir=in action=allow protocol=TCP localport=5900 remoteip=<source>

Inbound TCP 5900 (VNC / RFB). Set remoteip to a host/subnet; 'any' is discouraged.

netsh advfirewall firewall add rule name="Allow VNC / RFB 5900/UDP" dir=in action=allow protocol=UDP localport=5900 remoteip=<source>

Inbound UDP 5900 (VNC / RFB). Set remoteip to a host/subnet; 'any' is discouraged.

Windows PowerShell

New-NetFirewallRule -DisplayName "Allow VNC / RFB 5900/TCP" -Direction Inbound -Action Allow -Protocol TCP -LocalPort 5900 -RemoteAddress <source>

Inbound TCP 5900 (VNC / RFB). Replace <source> with a host or subnet.

New-NetFirewallRule -DisplayName "Allow VNC / RFB 5900/UDP" -Direction Inbound -Action Allow -Protocol UDP -LocalPort 5900 -RemoteAddress <source>

Inbound UDP 5900 (VNC / RFB). 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.