diff --git a/lib/cpp/src/transport/TSocket.cpp b/lib/cpp/src/transport/TSocket.cpp
index 58bb9f4..05fb35f 100644
--- a/lib/cpp/src/transport/TSocket.cpp
+++ b/lib/cpp/src/transport/TSocket.cpp
@@ -98,6 +98,10 @@
 }
 
 void TSocket::open() {
+  if (isOpen()) {
+    throw TTransportException(TTransportException::ALREADY_OPEN);
+  }
+
   // Create socket
   socket_ = socket(AF_INET, SOCK_STREAM, 0);
   if (socket_ == -1) {
diff --git a/lib/cpp/src/transport/TTransportException.h b/lib/cpp/src/transport/TTransportException.h
index 3ab1d66..d0cc59f 100644
--- a/lib/cpp/src/transport/TTransportException.h
+++ b/lib/cpp/src/transport/TTransportException.h
@@ -23,8 +23,9 @@
   enum TTransportExceptionType {
     UNKNOWN = 0,
     NOT_OPEN = 1,
-    TIMED_OUT = 2,
-    END_OF_FILE = 3,
+    ALREADY_OPEN = 2,
+    TIMED_OUT = 3,
+    END_OF_FILE = 4,
   };
   
   TTransportException() :