NPS5251
  1.  NetPortServer Compact 2 Port RS232/422/485 Device Server with Modbus and MQTT Support

The NPS5251 is a compact 2-port RS232/422/485 device server and IoT gateway for industrial use. It combines functions like serial device server, Modbus gateway, MQTT gateway, RS485-to-JSON gateway, and virtual COM port device tool. With two RS232 RJ45 ports, two RS485 terminal ports, and two Ethernet LAN ports, it ensures flexible and reliable connectivity. Its compact design supports desktop and DIN-rail installation, while the wide 10–30VDC power input or AC adapter enhances flexibility. The NPS5251 offers a cost-effective, space-saving solution.
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Modbus RTU /Ethernet Gateway

• Integrated Serial Port Server (Serial Device Server)
• Modbus RTU Server/ Client
• Modbus RTU to MQTT Gateway 
• Cloud JSON data to Modbus RTU 
• TCP Server/ Client, UDP, UDP Multicast
• TCP Server
• Auto-Polling Storage Multi Modbus/TCP Client to Single Modbus RTU Server
• Cloud Modbus/TCP to Modbus RTU Client Access
 

Modbus Gateway 

• Modbus RTU protocol to Modbus/TCP
• RTU/Register Auto Polling and Storage
• Allows Multiple points access same serial device
• Scheduling Polling Modbus RTU register 
 

JSON to Modbus RTU

• CSV JSON Table
• Scheduling Polling Modbus RTU register 
• Scheduling Publish in JSON format
• Subscribe support request and Setting Modbus Register

Modbus RTU to MQTT

• Publish RTU data in JSON format
• Subscribe JSON to Modbus RTU by HTTP Post, HTTP Get 
• NTP support for Network Time Synchronize


Serial Device Server

• TCP/UDP Transmission to virtual serial port
• Support Virtual COM Software tool 


Serial Interface

• Two RS232 DB9 RJ45 ports and Two RS422/485 Terminal ports
• Baud Rate – 1200bps ~460800bps, 5~9 data bit
• Parity Check – None, Odd, Even, Mark, Space


​Industrial Application

• DC 10~30V Power Input, Terminal Connector
• -25~70˚C / 5~95% RH Environment Operating Temperature
 
Step by Step
-Virtual COM Device Discovery and Management
-Device Setting
-Cloud MQTT Configuration
-Web Configuration
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Network Interface  

Ethernet 

Two 10/100M Ethernet RJ45
2KV Surge Protection
Serial Interface  
Connector

Two RS232 RJ45, Two RS422/485 Terminal
Serial Parameters

Baud Rate: 300~921600bps, Data Bit: 7~8
Parity Check: None, Odd, Even, Space, Mark
Flow Control: None Flow Control
Service Mode  
Virtual COM Driver Windows XP / Windows 7 / Windows 10/ Windows 11
TCP TCP Server for up to 30 TCP clients, or TCP client to up to 7 destination IP
UDP / UDP Multicasting UDP Polling & Response by UDP packet between stations 
UDP Multicast to all station by UDP packet
Modbus Modbus RTU to Modbus TCP
Modbus TCP to Modbus RTU
Cloud MQTT, JSON to Modbus RTU, HTTP Post, HPPT Get
Network Feature  
Protocol

Ethernet, IP, TCP, UDP, HTTP, ARP, ICMP, DHCP, DNS, Modbus
Security

TCP with authentication key
DHCP

DHCP Client for IP and DNS information from DHCP server
NTP Network Time Precision (NTP)
Management  
System Management Windows Utility, Virtual COM, WEB Management 
Windows DLL Library Device management function library (Windows DLL dynamic link library) by VC, VB, Delphi, or C++ Builder with functions such as read and write.
Power Input & Interface Connector
Power Input 10-30VDC Input, Terminal Block, DC Jack
Mechanical  & Installation  
Installation Din-Rail, Desktop
Enclosure Metal
IP Protection IP20
Dimension 94x65x25mm (LxWxH)
Environmental  
Operation Temperature -25°C~70°C, 0% ~ 90%, Non-Condensing
Storage Temperature -40°C~80°C, 0% ~ 90%, Non-Condensing
Reliability & Warranty  
MTBF > 200,000 Hours
Warranty 3 Year 
 
Model Description
NPS5251-E/U/UK Compact Two-port RS232/422/485 Device Server, Modbus, MQTT Gateway, 10~30Vdc
-Quick Installation Guide
-2 x RJ45 to DB9 male cable
-1 x 1m RJ45 cable
-Power Adapter (EU/US/UK)
-Din-rail Kit
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