Author Topic: Web Shield upload problem  (Read 1571 times)

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Web Shield upload problem
« on: September 10, 2017, 07:28:54 PM »
Using the Appinventor web based platform in 64bit Win7 Chrome Browser.

Larger Appinventor projects fail to upload with Avast Web Shield active.

I have noticed in the network section of the developer console of Google Chrome when Appinventor project XML data posted (uploaded) to the MIT server is larger than some 170kB the upload is pendning until a 2 min timeout.

If Avast Web Shield is turned off there is no problem with upload size. Much larger projects +1MB can be uploaded with no problem and upload takes only 1-3 seconds.

If project is reduced in size just removing repeated blocks making the XML payload smaller Avast Web Shield does not affect the upload.

Is the Web Shield bi-directional and interested in both uploads and downloads or is it a general timing issue due to Avast taping in to the network stream?

Is Avast intermediating the data and able to affect/damage what is uploaded?

If an upload is pending and Shield is turned off, the pending upload is aborted indicating Avast was part of the connection. After avast aborted and now disabled a new upload attempt without the Web Shield works fine.

I have tried all kind of exclusion settings using URL's but Avast effectively prevents a bit larger project XML uploads.

Update: Above problem applies to Win7, 64-bit Lenovo laptop. If same project is used on Win7 32-bit HP desktop also using Avast 17.6.2310 large files upload ok with Web Shield enabled.

Strange the 64-bit system does not work for files larger than 170kB but handles 1MB+ when Shield turned off??
« Last Edit: March 04, 2018, 02:14:48 AM by flodis »


  • Guest
Re: Web Shield upload problem
« Reply #1 on: September 13, 2017, 06:33:21 PM »
Here are some more interesting news:

When Avast is turned off a TCP packet sniffer reveals the first packet in a HTTP post is 881 bytes and consists of the a complete HTTP header for the HTTP POST operation. The rest of the upload data come in 1518 size TCP packages until upload completed.

When Avast Sheild is turned on and XML data uploaded is reasonably small 150kB or so - Avast stream data out in TCP packets all being of 1518 byte size.  That makes the HTTP header have some company followed by XML data in the first TCP package.

The veird thing is when the XML data in the POST is larger like 300kB the first and only TCP package on the AVAST output stream is 881 bytes long and then silence.

It looks like when Avast processes larger amount of data it gets to the first input stream TCP block and streams that out while the rest is lost, blocked or similar. Receiving server complains on the HTTP level after 30 seconds with error 500 as no more data was received. The TCP connection remains open until droped after 2 minutes with no more data sent.

Typical first TCP block data:
Code: [Select]
POST /ode/projects HTTP/1.1
Connection: keep-alive
Content-Length: 291796
X-GWT-Permutation: 94451607BB03FFFDB75CEAD85043BCBF
User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.113 Safari/537.36
Content-Type: text/x-gwt-rpc; charset=UTF-8
Accept: */*
Accept-Encoding: gzip, deflate
Accept-Language: sv-SE,sv;q=0.8,en-US;q=0.6,en;q=0.4,nb;q=0.2,de;q=0.2
Cookie: G_ENABLED_IDPS=google; _ga=GA1.2.1634098852.1504264096; AppInventor=..