Questions on Fiddler Forum

1 answer

2.0K+ views

Hello, I am trying to use FiddlerScript to change a json response from my API server to my client. I keep on getting an error when I have my client connect to the server. I am new to FiddlerScript so I don't know if I am doing anything wrong.

This is the code I am using in Fiddler ScriptEditor:

01.// Here is code to modify server's response

02.if(oSession.host == ("api.server") && oSession.uriContains("/config/url/1")) {

03. // Color this response, so we can spot it in Fiddler

04. oSession["ui-backcolor"] = "lime";

05.

06. // Convert the request body into a string

07. var oBody = System.Text.Encoding.UTF8.GetString(oSession.responseBodyBytes);

08.

09. // Convert the text into a JSON object

10. var j1 = Fiddler.WebFormats.JSON.JsonDecode(oBody);

11.

12. //Change the value

13. j1.JSONObject["data1"]["data2"]["data3"]["data4"]["Value"] = "1000";

14. j1.JSONObject["data1"]["data2"]["data3"]["Value"] = "1000";

15.

16. // Convert back to a byte array

17. var modBytes1 = Fiddler.WebFormats.JSON.JsonEncode(j1.JSONObject);

18.

19. // Convert json to bytes, storing the bytes in request body

20. var mod = System.Text.Encoding.UTF8.GetBytes(modBytes1);

21. oSession.RequestBody = mod;

22.}

23.

24.// Here is code to modify server's response

25.if(oSession.host == ("api.server") && oSession.uriContains("/config/url/2")) {

26. // Color this response, so we can spot it in Fiddler

27. oSession["ui-backcolor"] = "lime";

28.

29. // Convert the request body into a string

30. var oBody = System.Text.Encoding.UTF8.GetString(oSession.responseBodyBytes);

31.

32. // Convert the text into a JSON object

33. var j2 = Fiddler.WebFormats.JSON.JsonDecode(oBody);

34.

35. //Change the value

36. j2.JSONObject["data1"]["data2"]["data3"]["data4"]["Value"] = "1000";

37. j2.JSONObject["data1"]["data2"]["data3"]["Value"] = "1000";

38.

39. // Convert back to a byte array

40. var modBytes2 = Fiddler.WebFormats.JSON.JsonEncode(j2.JSONObject);

41.

42. // Convert json to bytes, storing the bytes in request body

43. var mod = System.Text.Encoding.UTF8.GetBytes(modBytes2);

44. oSession.RequestBody = mod;

45.}

46.

47.// Here is code to modify server's response

48.if(oSession.host == ("api.server") && oSession.uriContains("/config/database")) {

49. // Color this response, so we can spot it in Fiddler

50. oSession["ui-backcolor"] = "lime";

51. FiddlerApplication.Log.LogFormat(oBody);

52.

53. // Convert the request body into a string

54. var oBody = System.Text.Encoding.UTF8.GetString(oSession.responseBodyBytes);

55.

56. // Convert the text into a JSON object

57. var j3 = Fiddler.WebFormats.JSON.JsonDecode(oBody);

58.

59. //Change the value

60. j3.JSONObject["Value"] = "1";

61. j3.JSONObject["data1"]["Value"] = "1000";

62.

63. // Convert back to a byte array

64. var modBytes3 = Fiddler.WebFormats.JSON.JsonEncode(j3.JSONObject);

65.

66. // Convert json to bytes, storing the bytes in request body

67. var mod = System.Text.Encoding.UTF8.GetBytes(modBytes3);

68. oSession.RequestBody = mod;

69.}

70.

71.// Here is code to modify server's response

72.if(oSession.host == ("api.server") && oSession.uriContains("/config")) {

73. // Color this response, so we can spot it in Fiddler

74. oSession["ui-backcolor"] = "lime";

75.

76. // Convert the request body into a string

77. var oBody = System.Text.Encoding.UTF8.GetString(oSession.responseBodyBytes);

78.

79. // Convert the text into a JSON object

80. var j4 = Fiddler.WebFormats.JSON.JsonDecode(oBody);

81.

82. //Change the value

83. j4.JSONObject["Value"] = "1";

84. j4.JSONObject["data1"]["Value"] = "1000";

85.

86. // Convert back to a byte array

87. var modBytes4 = Fiddler.WebFormats.JSON.JsonEncode(j4.JSONObject);

88.

89. // Convert json to bytes, storing the bytes in request body

90. var mod = System.Text.Encoding.UTF8.GetBytes(modBytes4);

91. oSession.RequestBody = mod;

92.}

I have attached screenshots of the setup and the error codes.

Fiddler Classic

answered on 10 Mar 2020

1 answer

1.6K+ views

Can Fiddler be used to throttle an Android's or iPhone's network connections

I test mobile applications on both Android and iOS. I've tried using Fiddler running on a desktop PC to monitor an Android phone's network connections.

Can Fiddler running on a desktop PC be used not only to monitor an Android's or iPhone's network connections, but to throttle (slow down the speed, in a controlled manner) the mobile device's network connections? If so, how?

Thank you.

- Russell Johnson
Software Tester

Mobile

answered on 05 Mar 2020

1 answer

307 views

Fiddler keeping sockets open when in proxy mode

Hi,

I'm using Fiddler4 to capture from an iOS 13.3.1 device, with the iOS device set to Manual Proxy mode and necessary certificates installed on both end. Overall, works very well.

But there is a problem. For every socket opened by the iOS that goes via the proxy is never closed again. So the connection from iOS to Fiddler4 appears to be closed ok. However the socket from Fiddler4 to destination device stays open until I shutdown Fiddler.

The result of this is that on connection limited devices, they run out of available connections and it all stops working.

I've wiresharked the session when not going via Fiddler and iOS is correctly closing the socket (FIN state is sent).

When I wireshark the Fiddler4 proxied session the socket just stays open based on the socket is open from between my PC running Fiddler and the destination device.

Is this a known problem? If yes, is there a work around?

Best regards

Steve

Mobile

answered on 05 Mar 2020

9 answers

1.9K+ views

System wide Fiddler certificate on Ubuntu

Hello,

I just downloaded and installed Fiddler on my Ubuntu 16.04 machine (Love it on my Windows machine). Getting the Fiddler certificate installed for Chrome and Firefox was surprisingly easy (I thought I would have to do some converting).

However, when I try to add the same CER file to the system wide trusted certificates, my OS tells me that the FiddlerRoot.pem does not contain a certificate (output pasted below). I am wondering if this is a known issue since this is still in beta phase or if I am doing something wrong.

I am trying to do this so when I run things through the terminal Fiddler will pick them up - specifically HTTPS requests.

output:

test@GPA-HSW04:/usr/lib/mono/4.5$ sudo cp '/home/test/Desktop/FiddlerRoot.cer' '/usr/share/ca-certificates/FiddlerRoot.crt'
test@GPA-HSW04:/usr/lib/mono/4.5$ sudo dpkg-reconfigure ca-certificatesProcessing triggers for ca-certificates (20160104ubuntu1) ...
Updating certificates in /etc/ssl/certs...
WARNING: FiddlerRoot.pem does not contain a certificate or CRL: skipping

Linux

answered on 05 Mar 2020

5 answers

3.0K+ views

FiddlerCore free version

Which is the last version of FiddlerCore which is free for commercial use in a non public application?

Earlier I downloaded version 2.4.0.1

Is there any newer version which is free for commercial usage? If yes, from where can I download it?

FiddlerCore

answered on 04 Mar 2020

2 answers

3.0K+ views

Closing Fiddler Causes Internet Connect Loss

Hello. I've got tons of experience using Fiddler but it was on my old Windows 7 machine a couple years ago. I'm getting back to using Fiddler again, now on a Mac Book Pro, running Mojave. When I close Fiddler, whether by clicking the close icon on the window or selecting Quit from the menu, it causes my internet to be unusable. I get proxy errors in the browsers. I've followed directions to reset the proxies in system settings and this changes nothing. Obviously this is a game-breaking experience. Is there a solution?

Fiddler Everywhere

answered on 04 Mar 2020

0 answers

137 views

Fiddler dont show/find some connections

Hi guys,
I am pretty new on Fiddler and Wireshark and stuff like that. I try to edit a response for learning propose but many connections dont get Shown on Fiddler.
Like that one : "https://prnt.sc/r9a7ms"

May I messed something up with my settings or do I need to make some Script to get it working?

Thanks for your time guys.

Windows

asked on 28 Feb 2020

4 answers

4.0K+ views

Fiddler showing browser WebSockets, but not showing windows win32 app WebSocket connections?

Hi,

I am trying to capture WebSocket connection of an app in windows (Win32).

I also created a test app with websocketsharp and connected to ws://echo.websocket.org and unfortunately this was not captured in fiddler.

Any help?

Fiddler version: v5.0.20194.41348 for .NET 4.6.1
Built: Thursday, October 3, 2019

Windows

answered on 27 Feb 2020

1 answer

169 views

Remote traffic with port 443 encrypted

I have a tuned fiddler. It great was working before today morning.
I already had such a problem and it solved itself (i don't know how). I wasn't change settings, it just stopped decrypting.

Mobile

answered on 21 Feb 2020

1 answer

507 views

Error at startup. - Loading custom MIME mappings failed

---------------------------
Loading custom MIME mappings failed
---------------------------
Fiddler has encountered an unexpected problem. If you believe this is a bug in Fiddler, please copy this message by hitting CTRL+C, and submit a bug report at http://www.telerik.com/forums/fiddler.

The cloud file provider is not running.

Type: System.IO.IOException
Source: mscorlib
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)

at System.IO.FileStream.ReadCore(Byte[] buffer, Int32 offset, Int32 count)

at System.IO.FileStream.Read(Byte[] array, Int32 offset, Int32 count)

at System.Xml.XmlTextReaderImpl.InitStreamInput(Uri baseUri, String baseUriStr, Stream stream, Byte[] bytes, Int32 byteCount, Encoding encoding)

at System.Xml.XmlTextReaderImpl..ctor(String url, Stream input, XmlNameTable nt)

at System.Xml.Serialization.XmlSerializer.Deserialize(Stream stream)

at Fiddler.XmlFileMimeMappings..ctor(String filePath) in C:\Jenkins\Fiddler_Windows\workspace\Fiddler2\Common\Core\MimeMapping\XmlFileMimeMappings.cs:line 40

at Fiddler.frmViewer.(Object , EventArgs ) in C:\Jenkins\Fiddler_Windows\workspace\Fiddler2\Viewer.cs:line 9784

Fiddler v5.0.20194.41348 (x64 AMD64) [.NET 4.0.30319.42000 on Microsoft Windows NT 10.0.18362.0]
---------------------------
OK
---------------------------

Windows

answered on 21 Feb 2020