VB.NET: every second Modbus-Conection throws System.Net.Sockets.SocketException (0x80004005)

[Anonymous]

Hi together,

I use the EasyModbus.dll in a VB.NET project to read three DoubleRegisters every 15 minutes from two different devices (same model).
A few months everything was o.k. and the program could connectto the device via modbus and retrieve the values.
Then from one day to the other both devices now throw the following exception at every second(!) call:

In die Übertragungsverbindung können keine Daten geschrieben werden: Eine bestehende Verbindung wurde softwaregesteuert durch den Hostcomputer abgebrochen.: System.Net.Sockets.SocketException (0x80004005): Eine bestehende Verbindung wurde softwaregesteuert durch den Hostcomputer abgebrochen bei System.Net.Sockets.NetworkStream.Write(Byte[] buffer, Int32 offset, Int32 size)

I set the connection-period to 30 mins - the same. Then I read three additional double-registers and throw the values away - just to do a different call than before - the same effect: one call is o.k., the next one throws this error when I try to connect, the next one is ok, then exception... - identical for both devices...

Is this a known effect for some Modbus-servers that they reject a connection? What might be the reason?

Many thanks in advance
Michael

[Anonymous]