diff --git a/src/main/java/org/bdware/sc/ContractManager.java b/src/main/java/org/bdware/sc/ContractManager.java
index 6ef7a1b..5fe0161 100644
--- a/src/main/java/org/bdware/sc/ContractManager.java
+++ b/src/main/java/org/bdware/sc/ContractManager.java
@@ -1295,7 +1295,7 @@ public class ContractManager {
 
         long start = System.currentTimeMillis();
         // 9000
-        if (request.getRequester() != null && !request.getRequester().startsWith("event")) {
+        if (null != request.getRequester() && !request.getRequester().startsWith("event")) {
             if (client.contractMeta.sigRequired) {
                 if (!request.verifySignature()) {
                     cr = new ContractResult(Status.Error, new JsonPrimitive("sign verified failed"));
diff --git a/src/main/java/org/bdware/sc/event/EventCenter.java b/src/main/java/org/bdware/sc/event/EventCenter.java
index dc95d0e..17a678c 100644
--- a/src/main/java/org/bdware/sc/event/EventCenter.java
+++ b/src/main/java/org/bdware/sc/event/EventCenter.java
@@ -47,7 +47,7 @@ public class EventCenter {
         msg.setSemantics(semantics);
         msg.doSignature(instance.nodeCenterConn.getNodeKeyPair());
         String nodeId = getCenterByTopic(topic);
-        instance.masterStub.deliverEvent(JsonUtil.toJson(msg), nodeId);
+        instance.masterStub.deliverEvent(nodeId, JsonUtil.toJson(msg));
     }
 
     /**
@@ -62,18 +62,18 @@ public class EventCenter {
             return false;
         }
         String nodeId = getCenterByTopic(topic);
-        return instance.masterStub.deliverEvent(JsonUtil.toJson(event), nodeId);
+        return instance.masterStub.deliverEvent(nodeId, JsonUtil.toJson(event));
     }
 
     /**
      * publish an event to another node; used by NodeConsumer
      *
-     * @param eStr   event string
      * @param target id of the target node
+     * @param eStr   event string
      */
-    public void publishEvent(String eStr, String target) {
+    public void publishEvent(String target, String eStr) {
         if (null != instance.masterStub) {
-            instance.masterStub.deliverEvent(eStr, target);
+            instance.masterStub.deliverEvent(target, eStr);
         }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/bdware/sc/event/clients/ContractConsumer.java b/src/main/java/org/bdware/sc/event/clients/ContractConsumer.java
index 782d8e8..8fef7c0 100644
--- a/src/main/java/org/bdware/sc/event/clients/ContractConsumer.java
+++ b/src/main/java/org/bdware/sc/event/clients/ContractConsumer.java
@@ -75,10 +75,12 @@ public class ContractConsumer implements IEventConsumer {
         cr.setRequestID(options[0]);
         ContractClient cc = ContractManager.instance.getClient(contract);
         if (null == cc) {
+            LOGGER.error("contract " + contract + " doesn't exists!");
             rc.onResult((String) null);
             return;
         }
         AtomicInteger callCount = new AtomicInteger(0);
+        // TODO sending requests at a high frequency maybe cause that some requests are ignored
         ScheduledFuture<?> future = ContractManager.scheduledThreadPool.scheduleAtFixedRate(
                 () -> ContractManager.instance.executeContractInternal(cr, new ResultCallback() {
                     @Override
@@ -90,6 +92,7 @@ public class ContractConsumer implements IEventConsumer {
                                 if (callCount.get() == TIMEOUT_COUNT ||
                                         (result.status == ContractResult.Status.Exception &&
                                                 result.result.toString().contains("not exported"))) {
+                                    LOGGER.warn("receiving event error: request failed!");
                                     rc.onResult((String) null);
                                 } else {
                                     ret = false;
diff --git a/src/main/java/org/bdware/sc/event/clients/NodeConsumer.java b/src/main/java/org/bdware/sc/event/clients/NodeConsumer.java
index e9378e2..0fdeabb 100644
--- a/src/main/java/org/bdware/sc/event/clients/NodeConsumer.java
+++ b/src/main/java/org/bdware/sc/event/clients/NodeConsumer.java
@@ -33,7 +33,7 @@ public class NodeConsumer implements IEventConsumer {
 
     @Override
     public void publishEvent(Object msg, ResultCallback rc, String... options) {
-        center.publishEvent(msg.toString(), nodeId);
+        center.publishEvent(nodeId, msg.toString());
         if (null != rc) {
             rc.onResult("");
         }