With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
tn3270eTcpConnEntry
tn3270e Tcp Connection Entry
1.3.6.1.2.1.34.8.1.9.1
Provides information about a single TN3270/TN3270E session. Note: a tn3270eSrvrConfIndex is not needed in this table, since the combination of remote and local addresses and ports is sufficient to guarantee uniqueness across the TN3270E servers serviced by an SNMP agent. Because of this indexing structure, however, this table does not support view-based access control policies that provide access to table rows on a per-server basis.
Back to TN3270E-MIB MIB page.
IPHost Network monitor allows you to monitor tn3270eTcpConnEntry on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco routers right now.