Fix bug in send

Author: mitchellwrosen

changelog

@@ -2,6 +2,8 @@
   * Deprecate `NN_LINGER` option
   * Improve testsuite reliability
   * Add support for `NN_RCVMAXSIZE` option
+  * Fixed bug in nonblocking send where `threadWaitWrite` was used instead of
+    `threadWaitRead`
 
 0.2.4
   * Bumped upper bound on binary

src/Nanomsg.hsc

@@ -469,7 +469,7 @@ send (Socket t sid) string =
         throwErrnoIfMinus1RetryMayBlock_
             "send"
             (c_nn_send sid ptr (fromIntegral len) (#const NN_DONTWAIT))
-            (getOptionFd (Socket t sid) (#const NN_SNDFD) >>= threadWaitWrite)
+            (getOptionFd (Socket t sid) (#const NN_SNDFD) >>= threadWaitRead)
 
 -- | Blocking receive.
 recv :: Receiver a => Socket a -> IO ByteString