Port 9999Lantronix RS-485 Telnet Control
Port 9999 is commonly used by Lantronix device servers like the UDS-10 and UDS100 for remote Telnet configuration and management of serial-to-Ethernet converters, particularly those supporting RS-485 communication. This port allows network administrators to connect to the embedded Telnet service to configure network settings, serial parameters, or perform diagnostics on the device remotely..
- transport
- tcp
- in transit
- cleartext
- assignment
- unofficial
- risk
- 4/10
- lookups
- 15,770
single transport
payload readable on path
used by convention
caution
rank 194 of 993 · top 19%
2 other services are registered on port 9999. compare all 3 →
Technical Details
what runs on :9999Overview
Lantronix UDS series device servers provide a serial-to-Ethernet bridge that enables legacy RS-485 serial devices to be accessed over TCP/IP networks. These devices expose a Telnet management interface, typically running on TCP port 9999, facilitating configuration and control of the device's parameters remotely.
Protocol and Operation
The embedded Telnet server listens by default on TCP port 9999 and accepts plaintext commands from Telnet clients. Through this interface, users can:
- Assign network configuration parameters (IP address, gateway, etc.)
- Adjust serial communication settings (baud rate, parity, etc.)
- Manage operating modes such as transparent tunneling between serial and Ethernet
- Initiate diagnostics or firmware updates
The simplicity enables easy integration into network management workflows.
Ecosystem Integration
Port 9999 serves mainly during initial setup or troubleshooting of Lantronix UDS devices. In deployment, serial data is often tunneled through alternative dynamically configured ports, while the Telnet interface remains an auxiliary management channel, which can be optionally disabled after deployment for increased security.
Security Information
exposure of :9999risk score
4/ 10caution
worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.
network services averages 3.9 across 604 ports — this one sits 0.1 above.
in transit
cleartext
credentials and payloads are readable by anyone on path
assignment
unofficial
used by convention, not registered — what answers here varies by deployment
reachable over
tcp
every listening transport is another surface to filter at the edge
security overview
Common Vulnerabilities
- The Telnet protocol transmits data unencrypted, exposing passwords and configuration data to eavesdropping.
- Default or weak credentials could make devices susceptible to unauthorized access.
- Open port without proper access control may allow attackers to reconfigure devices, disrupt serial communications, or co-opt the device for malicious purposes.
- Older firmware may have unpatched vulnerabilities exploitable via Telnet session manipulation.
Common Mitigations
- Change all default Telnet access credentials and enforce strong passwords.
- Disable the Telnet service on port 9999 when not needed, or restrict access via network segmentation and firewalling.
- Use encrypted management alternatives (e.g., SSH if supported) instead of Telnet.
- Regularly update firmware to address known vulnerabilities.
- Deploy intrusion detection to monitor abnormal connection attempts to port 9999.
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| :3128 | Tatsoft Default HTTP Proxy | TCP | Web Services | caution | 46.8k |
risk mix of the 8 listed
- caution100%
0 of 8 encrypted