Using tshark to troubleshoot http

Here I give an example of how to use tshark, which is a command line tool and a part of the wireshark package, to monitor http requests and responses.

On Windows, first identify the numbering of the NIC adapters, using the '-D' option:

C:\Program Files\Wireshark>tshark.exe -D

1. \Device\NPF_GenericDialupAdapter (Adapter for generic dialup and VPN capture)

2. \Device\NPF_{2F15B435-C783-4863-90AC-C9DF8B64FBE1} (VMware Accelerated AMD PCNet Adapter)

Ok, lets now look at http traffic when loading the twitter home page:

C:\Program Files\Wireshark>tshark -i 2 "tcp port 80" -R "http.request or http.response"

Capturing on VMware Accelerated AMD PCNet Adapter

  0.005726 192.168.2.14 -> 199.59.150.39 HTTP 867 GET / HTTP/1.1

  3.067846 192.168.2.14 -> 199.59.150.39 HTTP 867 [TCP Retransmission] GET / HTTP/1.1

  4.577303 192.168.2.14 -> 184.169.78.33 HTTP 425 GET /a/1350941601/t1/css/t1_core_logged_out.bundle.css HTTP/1.1

  4.578931 192.168.2.14 -> 184.169.78.33 HTTP 414 GET /a/1350941601/t1/css/t1_more.bundle.css HTTP/1.1

  4.605371 199.59.150.39 -> 192.168.2.14 HTTP 279 HTTP/1.0 200 OK  (text/html)

  4.612847 184.169.78.33 -> 192.168.2.14 HTTP 615 HTTP/1.0 200 OK  (text/html)

  4.620900 184.169.78.33 -> 192.168.2.14 HTTP 593 HTTP/1.0 200 OK  (text/html)

  4.631572 192.168.2.14 -> 184.169.78.33 HTTP 414 GET /a/1350941601/images/bigger_spinner.gif HTTP/1.1

  4.631683 192.168.2.14 -> 184.169.78.33 HTTP 426 GET /a/1350941601/t1/img/front_page/city-balcony@2x.jpg HTTP/1.1

  4.634542 192.168.2.14 -> 184.169.78.33 HTTP 432 GET /c/swift/init.ef644480fe2a53578f7ce4eda13396e86b6fa74a.js HTTP/1.1

  4.679344 184.169.78.33 -> 192.168.2.14 HTTP 60 HTTP/1.0 200 OK  (GIF89a)

  4.679459 184.169.78.33 -> 192.168.2.14 HTTP 60 HTTP/1.0 200 OK  (GIF89a)

  4.683034 184.169.78.33 -> 192.168.2.14 HTTP 629 HTTP/1.0 200 OK  (text/html)

  4.702673 192.168.2.14 -> 199.59.150.39 HTTP 529 GET /opensearch.xml HTTP/1.1

  4.705784 199.59.150.39 -> 192.168.2.14 HTTP 417 HTTP/1.0 304 Not Modified

15 packets captured

You can see above, that this clearly shows the URLs to the html, image and css files that are downloaded from the server, and the associated http response codes.

Note the use of the tshark '-R' option to specify a "display" filter, to filter out everything, but the http requests and responses, so that we can concentrate on whats happening at the http level, without things like the tcp acks causing distraction. And you may want to expand the capture filter to just specify a particular host.