throw exception when no response received after timeout, fix the zmqSocket.send/recv exception handling

Signed-off-by: Leo Ma <[email protected]>

Author: leomaatEric

src/main/java/com/cisco/trex/stateless/TRexTransport.java

@@ -135,19 +135,21 @@ public synchronized String sendJson(String json) {
 
     byte[] compressed = this.dataCompressor.compressStringToBytes(json);
 
+    String response;
     try {
       zmqSocket.send(compressed);
+      byte[] msg = zmqSocket.recv();
+      response = this.dataCompressor.decompressBytesToString(msg);
     } catch (ZMQException e) {
       throw new IllegalStateException(
-          "Did not get any response from server "
-              + getHost()
-              + " within timeout "
-              + zmqSocket.getReceiveTimeOut(),
+          "Failed to send or recv json request or response due to ZMQ error: " + e.getErrorCode(),
           e);
     }
-    byte[] msg = zmqSocket.recv();
 
-    String response = this.dataCompressor.decompressBytesToString(msg);
+    if (response == null) {
+      throw new IllegalStateException(
+          "Got null json response, the reason could be get no response from server within timeout, or the ZMQ socket connection is in bad state either on client side or on server side.");
+    }
     LOGGER.debug("JSON Resp: {}", response);
     return response;
   }