By default, Http objects use Agent/SimpleTcp as transport agents
(section 41.1.4). They can also use Agent/FullTcp
agents, which allows Http objects to operate in a lossy network.
Class variable codeTRANSPORT_ is used for this purpose. E.g.,
Http set TRANSPORT
_ FullTcp tells all Http objects use FullTcp agents.
This configuration should be done before simulation starts, and it should not change during simulation, because FullTcp agents do not inter-operate with SimpleTcp agents.