Connection closed: how to find out which end-point is the cause

Question

In a C# application I have this code:

for (var i = 0; i < 10; i++)
{
    try
    {
        var op = operators[i]; // retrieve data
        plc.Modbus.WriteSingleRegister(MODBUS_TABLE_OP + i * 2, op.Id);
        plc.Modbus.WriteSingleRegister(MODBUS_TABLE_OP + i * 2 + 1, op.Password);
    }
    catch (Exception ex)
    {
        Logger.Error("Error: {0}", ex);
        throw;
    }
}

Where Modbus is an EasyModbus instance, and Id and Password are type int limited by software to 16-bit (i.e. op.Id = value & 0xFFFF). The code always ran fine, but since few days on the production machine after 4 or 5 iterations an exception is caught. This now happens every time the code runs. The exception message is:

Impossibile scrivere dati sulla connessione di trasporto: Connessione interrotta dal software del computer host

Unfortunately the production machine is set to Italian and I cannot change this setting. Nor I can run the code in debug mode on the production machine. Anyway, the most literal translation in English is:

Unable to write data on the transport connection: The connection was interrupted by the host computer software

I have difficult to understand the message itself, both in Italian and in English:

1. what does host computer mean in this context? The local machine (where the C# application runs) or the remote one?

2. what does software mean in this context? My software or a 'generic' one, like libraries or even the OS?

Without understanding these meanings I'm not able to figure out what has changed and where.

Update

Right know I can have the log of i and the op fields:

i    op.Id    op.Password
0    2        1111
1    5        1112
2    6        8765
3    7        0000
4    9        7877
// -> disconnection