Modbus TCP Master to a TCP Server

[sgsims]

Just trying to further my understanding of the different protocols and was wondering if someone could explain what is happening when I try the following.  I know it shouldn't work but just looking for a short layman's explanation of what is preventing the transmission from hapening.

I have an H0 Ecom100 in a DL06 (10.0.0.7) with a Peer table set up for a Modbus TCP Server (10.0.0.50) on Port502.

Instead of connecting the Ecom to a Modbus TCP Server i am connecting it to a PC (10.0.0.50) running Sockettest with a TCP Server listening on Port 502.

So I set up some ladder with an ECWX I-Box 741 and start sending those ECWX commands.

What I see on the sockettest utility is the following:

First: New Client: 10.0.0.7
Then:  Client Closed Connection

Like I said I realize this is sort of a silly post but nonetheless I am curious what is happening. I guess maybe the first thing that happens after the socket is opened is some sort of ack needs to be received by the client that tells the client that the server is indeed a Modbus TCP server.

Scott

[Greg]

Since the H0-ECOM100 is sending a TCP connection telegram to the PC (SocketTest app), you could see exactly what was happening with a free Ethernet packet sniffer on the same PC, like Wireshark. Download Wireshark (it's free), install, and then monitor and you can see exactly what is happening. My guess is a timeout.