--- title: Test RS232 Devices Using a Single Ethernet Port (Loop-back) description: Some applications may have limited access to ports for connecting and testing devices. Often times the most accessible is the Ethernet port. This is where... --- [Skip to content](https://support.gridconnect.com/grid-connect/test-rs232-devices-using-a-single-ethernet-port-loop-back#main-content) [Submit a ticket](https://support.gridconnect.com/grid-connect/kb-tickets/new?hsLang=en) ![Grid Connect](https://support.gridconnect.com/hubfs/GridConnect_FullColorLogo-2024.svg) Open main navigation Close main navigation - [Submit a ticket](https://support.gridconnect.com/grid-connect/kb-tickets/new) How can we help you? - There are no suggestions because the search field is empty. 1. [Grid Connect](https://support.gridconnect.com/grid-connect?hsLang=en) 2. [Grid Connect Products](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en) 3. [Testing and Evaluation](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en#testing-and-evaluation) # Test RS232 Devices Using a Single Ethernet Port (Loop-back) Some applications may have limited access to ports for connecting and testing devices. Often times the most accessible is the Ethernet port. This is where the Loop-back is useful.  **Note**: Before testing reset the adapter to factory settings. - Make sure your PC has an IP address in the same subnet as the serial adapter. - Connect your adapter to the Ethernet port of your PC or a connected switch.  - Connect pins 2 and 3 (Tx and Rx) of the serial DB-9 connector together using a wire. This creates the loop-back for the data. - Run Tera Term and open a Telnet connection to the IP address and Port of the serial adapter you are testing.  ![](https://support.gridconnect.com/hubfs/kb-migration/gridconnect/115014224207_mceclip1.png) - Type in the Terminal window and press enter. The characters you type will be sent out over the Ethernet connection to the adapter.  - **Note**: The characters will not appear in the window as you type. The window will only show data that has been received from the other end of the connection.  - When it reaches the serial connector, the data will be looped back through the wire between pins 2 and 3 of the DB-9 and sent back through the serial adapter to the terminal window.  - If the unit is working correctly with a complete connection, you will see the characters loop all the way back to the start and appear in the window.   - If the characters do not appear, - Make sure the connections on the loop-back have good contact with the terminals.  - Check the Ethernet cable connection. - Verify that the IP and Port are entered correctly. - Check power to the adapter. - Possibly a problem with the unit. - [Grid Connect Products](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en#main-content) - [Device Installer](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en#device-installer) - [Com Port](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en#com-port) - [GRIDBluFly](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en#gridblufly) - [NET485-01](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en#net485-01) - [Serial to Ethernet](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en#serial-to-ethernet) - [Serial over Bluetooth](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en#serial-over-bluetooth) - [xPort](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en#xport) - [CAN](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en#can) - [NET485-MB](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en#net485-mb) - [WI232+](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en#wi232) - [NET232+](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en#net232) - [Testing and Evaluation](https://support.gridconnect.com/grid-connect/grid-connect-products?hsLang=en#testing-and-evaluation) - [Distributed Vendors](https://support.gridconnect.com/grid-connect/distributed-vendors?hsLang=en#main-content) - [AKCP](https://support.gridconnect.com/grid-connect/distributed-vendors?hsLang=en#akcp) - [ATC](https://support.gridconnect.com/grid-connect/distributed-vendors?hsLang=en#atc) - [Chiyu](https://support.gridconnect.com/grid-connect/distributed-vendors?hsLang=en#chiyu) - [Deutschmann Automation](https://support.gridconnect.com/grid-connect/distributed-vendors?hsLang=en#deutschmann-automation) - [Equustek](https://support.gridconnect.com/grid-connect/distributed-vendors?hsLang=en#equustek) - [PEAK System](https://support.gridconnect.com/grid-connect/distributed-vendors?hsLang=en#peak-system) - [Profichip](https://support.gridconnect.com/grid-connect/distributed-vendors?hsLang=en#profichip) - [Zcomax](https://support.gridconnect.com/grid-connect/distributed-vendors?hsLang=en#zcomax) - [Procentec](https://support.gridconnect.com/grid-connect/distributed-vendors?hsLang=en#procentec) - [Contemporary Controls](https://support.gridconnect.com/grid-connect/distributed-vendors?hsLang=en#contemporary-controls) - [General](https://support.gridconnect.com/grid-connect/general?hsLang=en#main-content) - [FAQ](https://support.gridconnect.com/grid-connect/general?hsLang=en#faq) - [RS232](https://support.gridconnect.com/grid-connect/general?hsLang=en#rs232) - [Support](https://support.gridconnect.com/grid-connect/support?hsLang=en#main-content) - [How To guides](https://support.gridconnect.com/grid-connect/support?hsLang=en#how-to-guides) - [FAQs](https://support.gridconnect.com/grid-connect/support?hsLang=en#faqs) - [Troubleshooting](https://support.gridconnect.com/grid-connect/support?hsLang=en#troubleshooting) [![Grid Connect](https://support.gridconnect.com/hubfs/GridConnect_FullColorLogo-2024.svg "Grid Connect")](https://www.gridconnect.com/) Copyright © 2026, Grid Connect