Update

My patched version of Proxoid is available here: http://www.supermind.org/friends/SuperProxoid-debug.apk
Source code is available here: http://www.supermind.org/friends/superproxoid-snapshot-20101009.tar.gz

Note: I'm no longer using Proxoid, SuperProxoid, or even AziLink etc. I'm now using a rooted Android 2.2 which supports USB and wifi tethering! Way cool. Instructions here: http://www.supermind.org/blog/774/upgrade-your-htc-droid-eris-to-android-2-2

I've been using the excellent tether app, Proxoid to hook up my PC to my Android-based Droid Eris phone.

However, after a period of somewhat heavy usage/browsing, it inevitably barfs and refuses to take any more connections.

In Firefox, this appears as "Connection reset". In Chrome, pages simply refuse to load. The workaround I used for awhile was simply to stop the proxoid service on the Proxoid app, then start it again. This was fine (if somewhat annoying for surfing), but is a non-starter if you happen to be downloading anything at that point.

I decided to do abit of sleuthing, and installed the Log Collector app so I could see what was going on when Proxoid refused any more connections. Here's a snapshot of what the log file showed:

05-02 09:56:47.466 E/OSNetworkSystem( 6923): unclassified errno 24 (Too many open files)
05-02 09:56:47.466 E/OSNetworkSystem( 6923): unclassified errno 24 (Too many open files)
05-02 09:56:47.477 E/ProxoidService( 6923): null
05-02 09:56:47.477 E/ProxoidService( 6923): java.lang.NullPointerException
05-02 09:56:47.477 E/ProxoidService( 6923): at org.apache.harmony.nio.internal.SelectorImpl.prepareChannels(SelectorImpl.java:223)
05-02 09:56:47.477 E/ProxoidService( 6923): at org.apache.harmony.nio.internal.SelectorImpl.selectInternal(SelectorImpl.java:191)
05-02 09:56:47.477 E/ProxoidService( 6923): at org.apache.harmony.nio.internal.SelectorImpl.select(SelectorImpl.java:167)
05-02 09:56:47.477 E/ProxoidService( 6923): at com.mba.proxylight.RequestProcessor$1.run(RequestProcessor.java:72)
05-02 09:56:47.477 E/ProxoidService( 6923): at java.lang.Thread.run(Thread.java:1058)
05-02 09:56:47.486 E/ProxoidService( 6923): null
05-02 09:56:47.486 E/ProxoidService( 6923): java.net.SocketException: Operation failed
05-02 09:56:47.486 E/ProxoidService( 6923): at org.apache.harmony.luni.platform.OSNetworkSystem.createSocketImpl(Native Method)
05-02 09:56:47.486 E/ProxoidService( 6923): at org.apache.harmony.luni.platform.OSNetworkSystem.createSocket(OSNetworkSystem.java:85)
05-02 09:56:47.486 E/ProxoidService( 6923): at org.apache.harmony.nio.internal.SocketChannelImpl.(SocketChannelImpl.java:156)
05-02 09:56:47.486 E/ProxoidService( 6923): at org.apache.harmony.nio.internal.SelectorProviderImpl.openSocketChannel(SelectorProviderImpl.java:79)
05-02 09:56:47.486 E/ProxoidService( 6923): at java.nio.channels.SocketChannel.open(SocketChannel.java:95)
05-02 09:56:47.486 E/ProxoidService( 6923): at org.apache.harmony.nio.internal.ServerSocketChannelImpl.accept(ServerSocketChannelImpl.java:131)
05-02 09:56:47.486 E/ProxoidService( 6923): at com.mba.proxylight.RequestProcessor.process(RequestProcessor.java:351)
05-02 09:56:47.486 E/ProxoidService( 6923): at com.mba.proxylight.ProxyLight$1.run(ProxyLight.java:127)
05-02 09:56:47.486 E/ProxoidService( 6923): at java.lang.Thread.run(Thread.java:1058)
05-02 09:56:47.496 E/ProxoidService( 6923): null
05-02 09:56:47.496 E/ProxoidService( 6923): java.lang.NullPointerException
05-02 09:56:47.496 E/ProxoidService( 6923): at org.apache.harmony.nio.internal.SelectorImpl.wakeup(SelectorImpl.java:332)
05-02 09:56:47.496 E/ProxoidService( 6923): at com.mba.proxylight.RequestProcessor.closeAll(RequestProcessor.java:323)
05-02 09:56:47.496 E/ProxoidService( 6923): at com.mba.proxylight.RequestProcessor.access$2(RequestProcessor.java:302)
05-02 09:56:47.496 E/ProxoidService( 6923): at com.mba.proxylight.RequestProcessor$1.run(RequestProcessor.java:246)
05-02 09:56:47.496 E/ProxoidService( 6923): at java.lang.Thread.run(Thread.java:1058)
05-02 09:56:47.496 E/AndroidRuntime( 6923): Crash logging skipped, already logging another crash
05-02 09:56:47.496 E/OSNetworkSystem( 6923): unclassified errno 24 (Too many open files)

Huh. Too many open files. That would explain the non-response of Proxoid.

Googling for the offending line (org.apache.harmony.nio.internal.SelectorImpl.prepareChannels(SelectorImpl.java:223), yielded this: Selector leaks file descriptors in Apache Harmony. Yikes! Bad news.

The reporter of the bug in Android's issue tracker said:

Thanks for the quick answer. The workaround I used is quite simple: create as few
selectors as possible and recycle them endlessly.

I took a look at the Proxoid source and realized the error was fatal. A new selector is opened for each new request.

Its technically not a bug in Proxoid, but its awful to have to keep restarting Proxoid.

So I decided to hack a replacement proxy server implementation for Proxoid which uses threads instead of non-blocking IO. Took me 2 days to work everything out, and I ended up using some code from Muffin Proxy Server but it looks like things work fine. I tested my app out on 10000 HTTP requests (Proxoid barfed after about 1000) and no errors thus far. 🙂

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