SNMP functions

[berty_xx]

Hi,
I write program whitch read data from more industrial PC by SNMP. In program I use functions SnmpMgrOpen(agent, community, timeout, retries); SnmpMgrRequest(*session, requestType, &variableBindings,&errorStatus, &errorIndex) and SnmpMgrClose(*session).

Problem is in read data. From first 3 pc data is readed correctly, but from next pc no. Function return no error, but all value are NULL. In project are include library: mgmtapi.lib (3660 bytes), snmpapi.lib (8308 bytes) and advapi32.lib (117982 bytes). If I swap address of PC, data is always read from first 3 pc.
Structure of program is:

do{
session=Init SNMP (IP, community,...)
read all data from pc
Close SNMP(session)
}while( all PC )

Please help me.

Regards Peter