From 5a6228e9790da915d59312f75fd28e72c9f0c4a3 Mon Sep 17 00:00:00 2001
From: Mike Purvis <mpurvis@clearpathrobotics.com>
Date: Tue, 31 Jan 2017 14:39:10 -0500
Subject: [PATCH] In write_header() use poll if available. (#929)

---
 clients/rospy/src/rospy/impl/tcpros_base.py | 22 +++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/clients/rospy/src/rospy/impl/tcpros_base.py b/clients/rospy/src/rospy/impl/tcpros_base.py
index 134af0a1b0..7cb08686f1 100644
--- a/clients/rospy/src/rospy/impl/tcpros_base.py
+++ b/clients/rospy/src/rospy/impl/tcpros_base.py
@@ -613,11 +613,29 @@ def write_header(self):
             return
         fileno = sock.fileno()
         ready = None
-        while not ready:
-            _, ready, _ = select.select([], [fileno], [])
+        poller = None
+        if hasattr(select, 'poll'):
+            poller = select.poll()
+            poller.register(fileno, select.POLLOUT)
+            while not ready:
+                events = poller.poll()
+                for _, flag in events:
+                  if flag & select.POLLOUT:
+                        ready = True
+        else:
+            while not ready:
+                try:
+                    _, ready, _ = select.select([], [fileno], [])
+                except ValueError as e:
+                    logger.error("[%s]: select fileno '%s': %s", self.name, str(fileno), str(e))
+                    raise
+
         logger.debug("[%s]: writing header", self.name)
         sock.setblocking(1)
         self.stat_bytes += write_ros_handshake_header(sock, protocol.get_header_fields())
+        if poller:
+            poller.unregister(fileno)
+
 
     def read_header(self):
         """