Archive for May, 2017

 

HP Procurve MSM422 / MAP-625 clients flow the dhcp server [solved]

A client was using the HP Procurve MSM422 / MAP-625 MultiService Access Point (wifi). It was being used in a rather crowded wifi environment and the problem was the wifi clients keept reconnecting and renegotioating so often that the DHCP server was overflowed, sometimes with DHCP requests every few seconds. They had been struggling with the problem for a couple of months and the focus was aimed at the DHCP requests.

It turned out that the problem was not in the DHCP negotiation at all, but was caused by the wireless clients that keept losing connection and each time when they reconnected a DHCP request was sent.

The client was misinformed, that 5 GHz band was prohibited in the country where it was set up (which is acutally not). So both radios (radio 1 and 2) where set to 2,4 GHz where radio 1 was set to 802.11n/b/g and radio 2 with 802.11b/g.

Furthermore, for radio 2 the value of the Antenna gain was set to the maximum which is 29 dBi in an attempt to boost the maximum power out of the system. However, this field works the opposite. In order to be regulatory compliant and not emit more than the allowed power, this field informs the system that it is connected to an antenna with 29 dBi gain, so to not emit illegal levels of power (output power + antenna gain), the system will reduce the actual output power (i.e. the power input to the antenna) by 29 dBi. But the system was using the internal antennas which, I guess, has more or less no antenna gain. This caused the system to actually emit -29 dBi, i.e. a very weak wifi signal.

The low power output made it hard for the wifi clients to “hear” the access point, which caused them constantly to lose connection and when reconnecting, they were sending a DHCP request, hogging down the DHCP server.

Solution:

  • Radio 1 was configured to use the 5 GHz band. This band is much less crowded than the 2,4 GHz band and the bandwidth is better, so when a client has the possibility, it is preferred if it can use the 5 GHz band.
  • Radio 2 was configured to use Internal Antenna with 0 dBi antenna gain.

Settings used when the problem was solved like this (click on the image to enhance it):

HP Procurve MSM422 MAP-625

HP Procurve MSM422 MAP-625

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Posted by on May 31st, 2017 No Comments

“Not a valid image” when trying to upload images in Joomla! 3.7

Error message “Not a valid image” displayed when trying to upload an image in Joomla! 3.7. The error message is displayed even though the file type being uploded (jpg or png for example) is existing as valid type in both valid file types and mime types fields.

Solution: Go to System -> Global configuration -> Media and select Check MIME types = No

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Posted by on May 22nd, 2017 No Comments

PrestaShop 1.6 – unable to remove product from cart [solution]

If it’s not possible to remove an item from the cart in PrestaShop 1.6, try this solution:

Advanced settings -> Performance -> Move JavaScript to the end = NO

The problem seems to occur in Chrome and Microsoft Internet Explorer but not in other browsers like Firefox for example.

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Posted by on May 20th, 2017 No Comments

PrestaShop and PayPal payment error after checkout – 699 kr was paid instead of 699 kr [solved]

A client running PrestaShop 1.6.1.13 with PayPal payment module version 3.11.4 had problems after checkout of orders with an error message saying “699 kr was paid instead of 699 kr”. It turned out it was a rounding error where PrestaShop and PayPal use different methods of calculating the rounding.

The solution suggested was:

  • Go to preferences -> General
  • Rounding rule: Round to infinity when the value is halfway (recommended)
  • Rounding Type: Rounding for each element

This solved part of the problem. However, the client applied a store wide discount of 30%, causing a product (for example) costing 999 kr to checkout at 699 kr. To be precise, 999 kr minus 30% discount is 699,30 kr, but the 0,30 was rounded off. The same problem as mentioned above occured even when putting one piece of this item in the cart and checking it out.

It turned out that the theme used (jms_homewares version 1.0) only display prices in full kronor, without any decimals, independent of the settings regarding decimals in the Preferences -> General tab. In this case the settings was set to display 2 decimals. Setting it to 0 decimals solved the problem. I should mention that I am not sure if this is standard behavoiur of jms_homewares or if it has been modfied by the website developer. However, in this case setting it to display 0 decimals made everyting work without errors.

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Posted by on May 20th, 2017 No Comments

Joomla 3.7.0 error “Warning. Empty solution not allowed” when trying to save article in frontend [solution]

After upgrade to Joomla 3.7.0 an error was displayed when saving an article in the frontend. The error message was “Warning. Empty solution not allowed”.

The error message is a bit confusing, not giving any real hint what it is about. It turns out it has to do with Captcha. A new feature in Joomla 3.7.0 is the possibility to use Captcha on article editing.

To solve the problem, go to Options -> Articles and select the Editing Layout tab. Make sure “None Selected” is set in the Captcha field and click Save. Do click Save if it is already selected because it seems the setting is missing after the upgrade. By saving, the setting will be added and the problem is solved.

Joomla 3.7.0 "Warning. Empty solution not allowed"

Joomla 3.7.0 “Warning. Empty solution not allowed”

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Posted by on May 3rd, 2017 No Comments