diff --git a/lib/receiveData.js b/lib/receiveData.js
index e271d25..40cb152 100644
--- a/lib/receiveData.js
+++ b/lib/receiveData.js
@@ -35,7 +35,7 @@ module.exports = function (stream, timeout, responseLength, callback) {
     }
     // VALIDATE TERMINAL BYTE?
     stream.removeListener('data', handleChunk);
-    callback(err, buffer);
+    return callback(err, buffer);
   };
   if (timeout && timeout > 0) {
     timeoutId = setTimeout(function () {
@@ -44,4 +44,5 @@ module.exports = function (stream, timeout, responseLength, callback) {
     }, timeout);
   }
   stream.on('data', handleChunk);
+  return finished;
 };
diff --git a/lib/sendCommand.js b/lib/sendCommand.js
index 35c5d53..1928690 100644
--- a/lib/sendCommand.js
+++ b/lib/sendCommand.js
@@ -25,22 +25,23 @@ module.exports = function (stream, opt, callback) {
     cmd = Buffer.from(cmd.concat(Statics.Sync_CRC_EOP));
   }
 
-  stream.write(cmd, function (err) {
+  var finish = receiveData(stream, timeout, responseLength, function (err, data) {
     if (err) {
       error = new Error('Sending ' + cmd.toString('hex') + ': ' + err.message);
       return callback(error);
     }
-    receiveData(stream, timeout, responseLength, function (err, data) {
-      if (err) {
-        error = new Error('Sending ' + cmd.toString('hex') + ': ' + err.message);
-        return callback(error);
-      }
 
-      if (responseData && !data.equals(responseData)) {
-        error = new Error(cmd + ' response mismatch: '+data.toString('hex')+', '+responseData.toString('hex'));
-        return callback(error);
-      }
-      callback(null, data);
-    });
+    if (responseData && !data.equals(responseData)) {
+      error = new Error(cmd + ' response mismatch: '+data.toString('hex')+', '+responseData.toString('hex'));
+      return callback(error);
+    }
+    callback(null, data);
+  });
+
+  stream.write(cmd, function (err) {
+    if (err) {
+      error = new Error('Sending ' + cmd.toString('hex') + ': ' + err.message);
+      return finish(error);
+    }
   });
 };