To avoid warnings on some compilers, return NDN_ERROR_success instead of 0.
diff --git a/ndn-cpp/c/transport/socket-transport.c b/ndn-cpp/c/transport/socket-transport.c
index b4ded31..d48c794 100644
--- a/ndn-cpp/c/transport/socket-transport.c
+++ b/ndn-cpp/c/transport/socket-transport.c
@@ -62,7 +62,7 @@
 	freeaddrinfo(serverInfo);
   self->socketDescriptor = socketDescriptor;
 
-  return 0;
+  return NDN_ERROR_success;
 }
 
 ndn_Error ndn_SocketTransport_send(struct ndn_SocketTransport *self, unsigned char *data, unsigned int dataLength)
@@ -81,7 +81,7 @@
     dataLength -= nBytes;
   }
 
-  return 0;  
+  return NDN_ERROR_success;  
 }
 
 ndn_Error ndn_SocketTransport_receive
@@ -96,19 +96,19 @@
 
   *nBytesOut = (unsigned int)nBytes;
   
-	return 0;  
+	return NDN_ERROR_success;  
 }
 
 ndn_Error ndn_SocketTransport_close(struct ndn_SocketTransport *self)
 {
   if (self->socketDescriptor < 0)
     // Already closed.  Do nothing.
-    return 0;
+    return NDN_ERROR_success;
   
   if (close(self->socketDescriptor) != 0)
     return NDN_ERROR_SocketTransport_error_in_close;
   
   self->socketDescriptor = -1;
   
-  return 0;
+  return NDN_ERROR_success;
 }