Port 3696Telnet Com Port Control

Carries serial-port data and control over a Telnet connection, as used by RFC 2217-compatible serial device servers.

transport: tcp · udp
in transit: cleartext
assignment: official
risk: 2/10
lookups: 0

also known as telnetcpcd, RFC 2217, COM-PORT-OPTION

Technical Details

what runs on :3696

The assignment refers to Telnet Com Port Control, standardized as the RFC 2217 COM-PORT-OPTION (Telnet option 44). Over TCP, a client and server negotiate the Telnet option, then exchange serial data and subnegotiated commands for settings such as baud rate, parity, flow control, and modem signals; Telnet control bytes are escaped within the stream. TCP is the meaningful transport for this Telnet protocol. Although IANA lists UDP too, RFC 2217 does not define a standard UDP mode. Port 3696 is not a universal default for RFC 2217, so an open port alone does not confirm that this protocol is running.

Security Information

exposure of :3696

risk score

2/ 10safe

routine exposure. this port is rarely the way in on its own — keep it patched and logged and move on.

remote access averages 3.7 across 197 ports — this one sits 1.7 below.

in transit

cleartext

credentials and payloads are readable by anyone on path

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

tcp · udp

udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite

security overview

RFC 2217 provides no encryption or authentication of its own, so serial data and control may be exposed to interception or unauthorized use if a server is reachable without protection. Depending on what is attached to the serial port, access could expose a device console or let a client alter serial settings and signals. Do not expose an implementation directly to the internet; restrict access to trusted networks or protect it with a secure tunnel and suitable access controls.

Record

iana registry entry

port: :3696
service: Telnet Com Port Control
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 2/10safe
category: Remote Access Network Services
usage: This assignment is for Telnet Com Port Control, the RFC 2217 extension for accessing and controlling a serial port over a network connection. Engineers are more likely to encounter the protocol on a vendor-configured port on a serial device server than routinely find port 3696 open.
lookups: 0rank 993
added: 2026-10-01
updated: 2026-10-01
references: IANA service name registry — port 3696

Something wrong?

This record is maintained by the engineers who use port 3696. Every field on it is editable — change what's wrong, say how you know, and a reviewer publishes it, usually within a minute. Last touched 2026-10-01.

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edit this record →back to the registry

Related Ports

all 197 in remote access →

the 8 most looked-up other ports in remote access — 197 ports carry that label.

port	service	proto	category	risk	views
:8000	Intel Remote Desktop / Alternate HTTP Port	TCP	Web Services	safe	84.3k
:8888	D2GS Admin Console	TCP	Remote Access	caution	83.7k
:8881	Atlasz Secure Server	TCP	Web Services	caution	67.6k
:5938	TeamViewer	TCPUDP	Remote Access	caution	65.0k
:8291	Winbox MikroTik Admin	TCP	Security	caution	62.9k
:8008	IBM HTTP Server Admin	TCP	Web Services	caution	58.3k
:135	Microsoft EPMAP	TCPUDP	Security	caution	51.9k
:23	Telnet	TCP	Remote Access	caution	34.8k

risk mix of the 8 listed

safe13%
caution88%

0 of 8 encrypted

Port :3696Telnet Com Port Control

Technical Details

Security Information

Related Ports

Port 3696Telnet Com Port Control