IIS constantly takes 4 seconds to process the request from HTTP 1.0 client

[Svility]

I have a RFID reader (http://avea.cc/web08s.html), which posts the request to IIS server using GET method. Both the reader and server are placed in the same network and connected using a router. The reader posts the couple of paramaters using key/value pair and ASP.Net page will send the response using couple of tags (http://avea.cc/spec/web08s-sp01.pdf). I see a constant delay of 4 seconds to get the response on the reader. I see 4 seconds under the "time-taken" column in IIS logs. I have enabled failed request tracing and see "0ms" as processing time.There is no much code in ASP.Net page except sending hard-coded "GRNT=01" tags.I tried to send the same tags using PHP page, Classic ASP page on the same IIS server. But, still see the same 4 seconds delay.Below are the headers posted by reader:------------- HeaderParameters --------------Connection : closeUser-Agent : webreader (http://avea.cc)Then, I installed Ubuntu on the same Windows server using Hyper-V and pointed the reader to post to this new server. I got the response in fraction of a second. I used the same PHP file, which I used on IIS server. After that, I tried on couple of servers and I always got the delay on IIS and not on Non-IIS servers.No other roles are running on IIS server. Its a fresh installation with Web role. The delay is the same on Windows 7, Windows 8, Windows 2008 R2 and Windows 2012. I do not see any delay, when I post the same request through browser or Fiddler.Below is the log from Microsoft Network monitor:19 12:08:40 AM 9/18/2012 70.2321659 System 78.70.27.161 192.168.1.101 TCP TCP:Flags=......S., SrcPort=65269, DstPort=HTTP(80), PayloadLen=0, Seq=1498152, Ack=1023812214, Win=32768 ( ) = 32768 {TCP:12, IPv4:11}20 12:08:40 AM 9/18/2012 70.2341408 System 192.168.1.101 78.70.27.161 TCP TCP:Flags=...A..S., SrcPort=HTTP(80), DstPort=65269, PayloadLen=0, Seq=1500184337, Ack=1498153, Win=8192 ( Scale factor not supported ) = 8192 {TCP:12, IPv4:11}21 12:08:40 AM 9/18/2012 70.3629428 System 78.70.27.161 192.168.1.101 HTTP HTTP:Request, GET /avea.asp, Query:cmd=PU&sid=00000100&deviceid=5988&mac=00:13:00:00:17:64&id=192.168.1.100&type=m&mode=MF2&rev=2&sw=O&ver=1.23 {HTTP:13, TCP:12, IPv4:11}22 12:08:40 AM 9/18/2012 70.3636151 System 192.168.1.101 78.70.27.161 HTTP HTTP:Response, HTTP/1.1, Status: Ok, URL: /avea.asp {HTTP:13, TCP:12, IPv4:11}23 12:08:40 AM 9/18/2012 70.7728540 System 192.168.1.101 78.70.27.161 TCP TCP:[ReTransmit #22]Flags=...AP..F, SrcPort=HTTP(80), DstPort=65269, PayloadLen=251, Seq=1500184338 - 1500184590, Ack=1498347, Win=65070 (scale factor 0x0) = 65070 {TCP:12, IPv4:11}24 12:08:41 AM 9/18/2012 71.5462335 System 192.168.1.101 78.70.27.161 TCP TCP:[ReTransmit #22]Flags=...AP..F, SrcPort=HTTP(80), DstPort=65269, PayloadLen=251, Seq=1500184338 - 1500184590, Ack=1498347, Win=65070 (scale factor 0x0) = 65070 {TCP:12, IPv4:11}25 12:08:43 AM 9/18/2012 73.1113701 System 192.168.1.101 78.70.27.161 TCP TCP:[ReTransmit #22]Flags=...AP..F, SrcPort=HTTP(80), DstPort=65269, PayloadLen=251, Seq=1500184338 - 1500184590, Ack=1498347, Win=65070 (scale factor 0x0) = 65070 {TCP:12, IPv4:11}26 12:08:43 AM 9/18/2012 73.2449081 System 78.70.27.161 192.168.1.101 HTTP HTTP:Request, GET /avea.asp, Query:cmd=PU&sid=00000100&deviceid=5988&mac=00:13:00:00:17:64&id=192.168.1.100&type=m&mode=MF2&rev=2&sw=O&ver=1.23 {HTTP:13, TCP:12, IPv4:11}27 12:08:43 AM 9/18/2012 73.4495140 System 192.168.1.101 78.70.27.161 TCP TCP:Flags=...A...., SrcPort=HTTP(80), DstPort=65269, PayloadLen=0, Seq=1500184590, Ack=1498541, Win=64876 (scale factor 0x0) = 64876 {TCP:12, IPv4:11}28 12:08:44 AM 9/18/2012 74.6766982 System 192.168.1.101 78.70.27.161 TCP TCP:[ReTransmit #22]Flags=...AP..F, SrcPort=HTTP(80), DstPort=65269, PayloadLen=251, Seq=1500184338 - 1500184590, Ack=1498541, Win=64876 (scale factor 0x0) = 64876 {TCP:12, IPv4:11}29 12:08:44 AM 9/18/2012 74.7931629 System 78.70.27.161 192.168.1.101 TCP TCP:Flags=...A...F, SrcPort=65269, DstPort=HTTP(80), PayloadLen=0, Seq=1498541, Ack=1500184590, Win=32768 (scale factor 0x0) = 32768 {TCP:12, IPv4:11}30 12:08:44 AM 9/18/2012 74.7931982 System 192.168.1.101 78.70.27.161 TCP TCP:Flags=...A...., SrcPort=HTTP(80), DstPort=65269, PayloadLen=0, Seq=1500184590, Ack=1498542, Win=64876 (scale factor 0x0) = 64876 {TCP:12, IPv4:11}Below is the corresponding entry in IIS Logs:#Software: Microsoft Internet Information Services 7.5#Version: 1.0#Date: 2012-09-18 12:00:28#Fields: date time cs-method cs-uri-stem cs-uri-query c-ip cs-version cs(User-Agent) cs(Cookie) cs(Referer) sc-status sc-substatus sc-win32-status time-taken2012-09-18 12:08:44 GET /avea.asp cmd=PU&sid=00000100&deviceid=5988&mac=00:13:00:00:17:64&id=192.168.1.100&type=m&mode=MF2&rev=2&sw=O&ver=1.23 78.70.27.161 HTTP/1.0 webreader+(http://avea.cc) - - 200 0 0 4421On the same windows box, if I use Apache+PHP, there is no delay.On the same network, with Ubuntu+PHP, there is no delay.Please let me know if you have any suggestions to reduce the delay.Thank you for your time!