Unknown app using the Internet

Discussion in 'macOS' started by drewc1138, Mar 13, 2010.

  1. drewc1138 macrumors 6502

    Joined:
    Jun 30, 2007
    #1
    I'm having an issue with something on my iMac using up my bandwidth on my home network.*

    Over the past few days I've noticed that my Internet has been CRAWLING. I did a speedtest.net test, and the download was about normal, but the upload speed was anywhere between 3 kbps and 15 kbps, instead of my usual 300 kbps (not stellar, I know, but it's the best I can get). When I look at my wireless router, the indicator light for Ethernet is constantly flashing, showing that there is some activity, even though nothing is happening. I will even go in and close out every app, do a complete restart even, and something continues to use it up. When I shut down my iMac, the upload speed jumps back up to normal on my MacBook and iPhone, but when it's restarted, it slows to pre-dialup speeds again, so I know that it's something on the iMac.*

    I just don't know how to find it. I've tried poking around in the Activity Monitor, but I don't find anything too out of place. I'm sure there's a simple fix, I just don't know what it is. Any suggestions would be appreciated.*
     
  2. JNB macrumors 604

    JNB

    Joined:
    Oct 7, 2004
    Location:
    In a Hell predominately of my own making
    #2
    What kind of connection do you have (Cable, DSL, satellite)? Is the modem showing the same activity?
     
  3. drewc1138 thread starter macrumors 6502

    Joined:
    Jun 30, 2007
    #3
    Cable, and yes, the modem is showing the same.
     
  4. JNB macrumors 604

    JNB

    Joined:
    Oct 7, 2004
    Location:
    In a Hell predominately of my own making
    #4
    The basic answer is that cable is a shared connection, and as such, you should pretty much always see a bunch of traffic across it. It may not be destined for you, but you're seeing all the other stuff in your neighborhood. Also, as a shared connection, the total bandwidth advertised is a maximum a user may see with minimal other traffic; if everybody in the neighborhood is streaming or downloading a lot, it'll toast your bandwidth.

    To see this in action, try turning off all of your internet-connected devices, you'll still see the modem going like gangbusters, especially in the evenings.
     
  5. drewc1138 thread starter macrumors 6502

    Joined:
    Jun 30, 2007
    #5
    That's just the thing...if I take my iMac off of the network, everything else runs smoothly.

    I have my iMac plugged directly into my linksys router through ethernet. When it's plugged in, everything crawls.

    If I unplug the iMac, everything that connects wirelessly starts working perfectly. If I connect the iMac to the network over WiFi, everything starts crawling again. If I unplug the ethernet from the router and plug it directly from my modem into the iMac, it crawls. If I do the same and plug directly into my MacBook, it flies. Anytime the iMac is NOT on the network, the PC/Activity indicator on my modem is solid. Anytime the iMac IS connected, it's going, as you said, like gangbusters.

    I get what you're saying about bottlenecking and all that, but it just seems like every piece of evidence points to this being an issue with my iMac.
     
  6. robert05au macrumors regular

    robert05au

    Joined:
    May 19, 2005
    Location:
    Dubbo, NSW
    #6
    I have something to try which may help work out if it is the imac or a setting in the router.

    Open System Preferences/Network with the connection to the imac show the dhcp with the ip number and router info. Click renew release.

    This causes the connection to get a new lease from the router.

    Lets know if that makes any even a small difference.

    If that doesn't work try this

    open the terminal and type or copy and paste the following

    sudo dscacheutil -flushcache

    you will need to enter your admin password for it to work.

    Lets know what happens and I will help further as I have used Linksys router in the past and seen a few strange issues with slow connection.
     
  7. JNB macrumors 604

    JNB

    Joined:
    Oct 7, 2004
    Location:
    In a Hell predominately of my own making
    #7
    Have you looked at Activity Monitor to see what processes are running that may be the cause? Also, take a look at the Login Items for your user for anything that you may have installed that could be constantly generating network activity. Lastly, consider (temporarily) creating a new Standard User account, start up logging into that and see if the problem persists.
     
  8. Ganesha macrumors regular

    Joined:
    Aug 4, 2009
    #8
    A Terminal Command to try

    lsof | grep IPv4

    This will list all applications that have an open internet connection. My advice close down everything you expect to use the internet on the iMac, plug it into a wired network connection, then use this command.
     
  9. dav146 macrumors regular

    dav146

    Joined:
    Dec 21, 2007
    #9
    Get a Program called 'Little Snitch' on your offending machine.

    The program will query every outbound internet connection (from that particular mac). If something is trying to talk - Little Snitch will make you aware of it.

    http://www.obdev.at/products/littlesnitch/index.html

    You get a 3 hour free trial, afterwards you should pay 30 euros to get the proper serial / license.
     
  10. drewc1138 thread starter macrumors 6502

    Joined:
    Jun 30, 2007
    #10
    Tried everything that you said, Robert, and something worked, because it's doing much better now. Thanks, guys!
     
  11. hakuryuu macrumors 6502

    Joined:
    Sep 30, 2007
    Location:
    Lomita, CA
    #11
    I have to second this. greatest little tool.
     

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