Add Application-level Keepalive

ExternalIO/client.py

@@ -1,7 +1,34 @@
+import platform
 import socket, ssl
 import struct
 import time
 
+# The following function is either taken directly or derived from:
+# https://stackoverflow.com/questions/12248132/how-to-change-tcp-keepalive-timer-using-python-script
+def set_keepalive_linux(sock, after_idle_sec=1, interval_sec=3, max_fails=5):
+    """Set TCP keepalive on an open socket.
+
+    It activates after 1 second (after_idle_sec) of idleness,
+    then sends a keepalive ping once every 3 seconds (interval_sec),
+    and closes the connection after 5 failed ping (max_fails), or 15 seconds
+    """
+    sock.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
+    sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPIDLE, after_idle_sec)
+    sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPINTVL, interval_sec)
+    sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPCNT, max_fails)
+
+# The following function is either taken directly or derived from:
+# https://stackoverflow.com/questions/12248132/how-to-change-tcp-keepalive-timer-using-python-script
+def set_keepalive_osx(sock, after_idle_sec=1, interval_sec=3, max_fails=5):
+    """Set TCP keepalive on an open socket.
+
+    sends a keepalive ping once every 3 seconds (interval_sec)
+    """
+    # scraped from /usr/include, not exported by python's socket module
+    TCP_KEEPALIVE = 0x10
+    sock.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
+    sock.setsockopt(socket.IPPROTO_TCP, TCP_KEEPALIVE, interval_sec)
+
 class Client:
     def __init__(self, hostnames, port_base, my_client_id):
         ctx = ssl.SSLContext()
@@ -22,6 +49,13 @@ class Client:
                         time.sleep(1)
                     else:
                         raise
+                    
+            if platform.system() == "Linux":
+                set_keepalive_linux(plain_socket)
+            elif platform.system() == "Darwin":
+                set_keepalive_osx(plain_socket)
+
+            set_keepalive_linux(plain_socket)
             octetStream(b'%d' % my_client_id).Send(plain_socket)
             self.sockets.append(ctx.wrap_socket(plain_socket,
                                                 server_hostname='P%d' % i))