diff --git a/src/calibre/srv/http_request.py b/src/calibre/srv/http_request.py
index e6684c2079..c020e5bdc2 100644
--- a/src/calibre/srv/http_request.py
+++ b/src/calibre/srv/http_request.py
@@ -154,7 +154,6 @@ class HTTPRequest(Connection):
 
     def __init__(self, *args, **kwargs):
         Connection.__init__(self, *args, **kwargs)
-        self.corked = False
         self.max_header_line_size = int(1024 * self.opts.max_header_line_size)
         self.max_request_body_size = int(1024 * 1024 * self.opts.max_request_body_size)
 
diff --git a/src/calibre/srv/http_response.py b/src/calibre/srv/http_response.py
index afbd11fe2a..aa2d3313be 100644
--- a/src/calibre/srv/http_response.py
+++ b/src/calibre/srv/http_response.py
@@ -7,10 +7,6 @@ __license__ = 'GPL v3'
 __copyright__ = '2015, Kovid Goyal <kovid at kovidgoyal.net>'
 
 import os, httplib, hashlib, uuid, zlib, time, struct, repr as reprlib
-try:
-    from select import PIPE_BUF
-except ImportError:
-    PIPE_BUF = 512  # windows
 from collections import namedtuple
 from io import BytesIO, DEFAULT_BUFFER_SIZE
 from itertools import chain, repeat, izip_longest
@@ -23,7 +19,7 @@ from calibre.srv.loop import WRITE
 from calibre.srv.errors import HTTP404
 from calibre.srv.http_request import HTTPRequest, read_headers
 from calibre.srv.sendfile import file_metadata, sendfile_to_socket_async, CannotSendfile, SendfileInterrupted
-from calibre.srv.utils import MultiDict, start_cork, stop_cork, http_date, HTTP1, HTTP11, socket_errors_socket_closed
+from calibre.srv.utils import MultiDict, http_date, HTTP1, HTTP11, socket_errors_socket_closed
 from calibre.utils.monotonic import monotonic
 
 Range = namedtuple('Range', 'start stop size')
@@ -283,7 +279,7 @@ class HTTPConnection(HTTPRequest):
                 self.use_sendfile = self.ready = False
                 raise IOError('sendfile() failed to write any bytes to the socket')
         else:
-            sent = self.send(buf.read(min(limit, PIPE_BUF)))
+            sent = self.send(buf.read(min(limit, self.send_bufsize)))
         buf.seek(pos + sent)
         return buf.tell() == end
 
@@ -367,8 +363,7 @@ class HTTPConnection(HTTPRequest):
 
     def response_ready(self, header_file, output=None):
         self.response_started = True
-        start_cork(self.socket)
-        self.corked = True
+        self.optimize_for_sending_packet()
         self.use_sendfile = False
         self.set_state(WRITE, self.write_response_headers, header_file, output)
 
@@ -437,8 +432,7 @@ class HTTPConnection(HTTPRequest):
     def reset_state(self):
         self.connection_ready()
         self.ready = not self.close_after_response
-        stop_cork(self.socket)
-        self.corked = False
+        self.end_send_optimization()
 
     def report_unhandled_exception(self, e, formatted_traceback):
         self.simple_response(httplib.INTERNAL_SERVER_ERROR)
diff --git a/src/calibre/srv/loop.py b/src/calibre/srv/loop.py
index 05ae578950..95993c16cc 100644
--- a/src/calibre/srv/loop.py
+++ b/src/calibre/srv/loop.py
@@ -14,17 +14,20 @@ from calibre import as_unicode
 from calibre.ptempfile import TemporaryDirectory
 from calibre.srv.opts import Options
 from calibre.srv.utils import (
-    socket_errors_socket_closed, socket_errors_nonblocking, HandleInterrupt, socket_errors_eintr)
+    socket_errors_socket_closed, socket_errors_nonblocking, HandleInterrupt,
+    socket_errors_eintr, start_cork, stop_cork)
 from calibre.utils.socket_inheritance import set_socket_inherit
 from calibre.utils.logging import ThreadSafeLog
 from calibre.utils.monotonic import monotonic
 
 READ, WRITE, RDWR = 'READ', 'WRITE', 'RDWR'
+DESIRED_SEND_BUFFER_SIZE = 16 * 1024
 
 class Connection(object):
 
     def __init__(self, socket, opts, ssl_context, tdir):
         self.opts = opts
+        self.orig_send_bufsize = self.send_bufsize = 4096
         self.tdir = tdir
         self.ssl_context = ssl_context
         self.wait_for = READ
@@ -39,6 +42,22 @@ class Connection(object):
             self.connection_ready()
         self.last_activity = monotonic()
 
+    def optimize_for_sending_packet(self):
+        start_cork(self.socket)
+        self.orig_send_bufsize = self.send_bufsize = self.socket.getsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF)
+        if self.send_bufsize < DESIRED_SEND_BUFFER_SIZE:
+            try:
+                self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF, DESIRED_SEND_BUFFER_SIZE)
+            except socket.error:
+                pass
+            else:
+                self.send_bufsize = self.socket.getsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF)
+
+    def end_send_optimization(self):
+        stop_cork(self.socket)
+        if self.send_bufsize != self.orig_send_bufsize:
+            self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF, self.orig_send_bufsize)
+
     def set_state(self, wait_for, func, *args, **kwargs):
         self.wait_for = wait_for
         if args or kwargs:
diff --git a/src/calibre/srv/tests/http.py b/src/calibre/srv/tests/http.py
index 02bc2e96a8..c4e4d6daaf 100644
--- a/src/calibre/srv/tests/http.py
+++ b/src/calibre/srv/tests/http.py
@@ -329,6 +329,6 @@ class TestHTTP(BaseTest):
                 self.ae(len(data), len(rdata))
                 self.ae(hashlib.sha1(data).hexdigest(), hashlib.sha1(rdata).hexdigest())
                 self.ae(data, rdata)
-                self.assertLess(monotonic() - start_time, 5, 'Large file transfer took too long')
+                self.assertLess(monotonic() - start_time, 1, 'Large file transfer took too long')
 
     # }}}