How can I establish multiple TCP Connections to the NCD5500?

We are using the P420RL boards that needs to be accessed by two separate computers on our network. When I run my script that connects to the board and pulls the ADC values, everything works fine. If I open NCD Base and connect to the board, my script gets the error that no connection could be made because the target machine actively refused it. As soon as I close NCD Base, the script carries on as normal. It appears as though the NCD5500 is only allowing 1 TCP connection at a time. How can I enable 2 simultaneous connections? I thought possibly changing to UDP, but it appears that is broadcast only, and to a single host, and wasn’t receiving commands.

Hi Joe,

The Ethernet interface module only allows 1 simultaneous TCP socket connection at a time.

Typically if it is required to communicate with the device from multiple software applications there are two ways I recommend. First only connect to the device when communication is necessary. So connect, send command, get response, then disconnect. This allows multiple applications. to communicate without consuming the socket at all times.
The second alternative is to have 1 software application establish a connection to the board and communicate with it. Then other software applications communicate with that server application and communicate with the board by sending commands to that primary software application.

If you have any other questions please let us know.

Thank you,

Yikes. Not what I was hoping to hear. We just bought 21 of these, i hope we will still be able to use them. Any chance of a firmware update that can enable a second TCP connection? Or even allowing multiple UDP connections would work as well.


No, it is not possible to update the firmware. This is a limitation of the embedded Ethernet interface module.

UDP could be used, the device can be set to listen on a UDP port and can be configured to broadcast( to send data back.