Fix METADAPT-A not receiving more than one message

metadapta.go

@@ -102,7 +102,7 @@ func (this *a) receive() {
 	defer func() {
 		this.underlying.Close()
 		this.transLock.Lock()
-		defer this.transLock.Lock()
+		defer this.transLock.Unlock()
 		for _, trans := range this.transMap {
 			trans.Close()
 		}
@@ -124,22 +124,30 @@ func (this *a) receive() {
 }
 
 func (this *a) receiveMultiplex(transID int64, method uint16, payload []byte) error {
-	if transID == 0 || this.party == partyFromTransID(transID) {
+	if transID == 0 { return ErrMessageMalformed }
-		return ErrMessageMalformed
-	}
 
+	trans, err := func() (*transA, error) {
 		this.transLock.Lock()
 		defer this.transLock.Unlock()
 
 		trans, ok := this.transMap[transID]
 		if !ok {
+			// it is forbidden for the other party to initiate a transaction
+			// with an ID from this party
+			if this.party == partyFromTransID(transID) {
+				return nil, ErrMessageMalformed
+			}
 			trans = &transA {
 				parent:   this,
 				id:       transID,
 				incoming: usync.NewGate[incomingMessage](),
 			}
+			this.transMap[transID] = trans
 			this.transChan <- trans
 		}
+		return trans, nil
+	}()
+	if err != nil { return err }
 
 	trans.incoming.Send(incomingMessage {
 		method:  method,