AgentX: subAgent does not respond to master agent

Hi,
 
I started snmpd as the master agent with agentxsocket set as udp:705. In my subagent embeded in another application runing at the same linux box, I set the same. When I start the subagent, I can see that they communicate to each other. Handlers for some enterprise MIB OID's are registered. For example the subagent print out:
 
agentx/subagent: registering: iso.3.6.1.4.1.6393.5.1.3.2.1.1.2
agentx_build: packet built okay
agentx/subagent: synching input, op 0x01
agentx/subagent: registered

and on the other hand, the masterAgent(snmpd) print out: 
 
agentx/master: handle pdu (req=0x1c472f35,trans=0x0,sess=0x4)
agentx/master: in register_agentx_list
agentx/master: registered ok
agentx/master: send response, stat 0 (req=0x1c472f35,trans=0x0,sess=0x4)
agentx_build: packet built okay

However when I try snmp get, the master agent received correct information and trying to pass it to the subagent, but the subagent does not respond. This is what printed by the master agent:
 
Received SNMP packet(s) from UDP: [192.168.1.126]:3629
  GET message
    -- iso.3.6.1.4.1.6393.5.1.3.2.1.1.2.0
agentx/master: agentx master handler starting, mode = 0xa0
agentx/master: request for variable (iso.3.6.1.4.1.6393.5.1.3.2.1.1.2.0)
agentx: sending pdu (req=0xd,trans=0xc,sess=0x4)
agentx_build: packet built okay

Nothing print out by the SubAgent with "agentx" token turned on, as if the request is not reach the subAgent. Ping message between the master and Subagent seems working.