问Corda - SignTransactionFlow和sendAndReceive

EN

class TestContract : Contract{
    companion object{
        @JvmStatic
        val ID = "package net.corda.sample.TestContract"
    }
    override fun verify(tx: LedgerTransaction) {

    }
}
@BelongsToContract(TestContract::class)
class TestState(val owner : Party, val value : String) : ContractState {
    override val participants: List<AbstractParty>
        get() = listOf(owner)
}


@InitiatingFlow
@StartableByRPC
class receiveStateFlow(private val counterparty: Party) : FlowLogic<Unit>() {
    override val progressTracker = ProgressTracker()
    val log = loggerFor<receiveStateFlow>()

    @Suspendable
    override fun call() {
        val counterpartySession = initiateFlow(counterparty)
        val counterpartyData = counterpartySession.sendAndReceive<TestState>("hello")
        counterpartyData.unwrap { msg ->
            log.warn(msg.value)
            assert((msg.participants.first()) == counterparty)
        }
    }
}

@InitiatedBy(receiveStateFlow::class)
class sendStateFlow(private val counterpartySession: FlowSession) : FlowLogic<Unit>() {
    @Suspendable
    override fun call() {
        val counterpartyData = counterpartySession.receive<String>()
        counterpartyData.unwrap { msg ->
            assert(msg == "hello")
        }
        val newState = TestState(serviceHub.myInfo.legalIdentities.first(), "someValue")
        counterpartySession.send(newState)
    }
}