title: What are some reasons why Composer will fail to connect to packagist through http, if not behind a firewall or proxy?
body: <p>I have been trying to use Composer on Centos 5.5. I managed to install it, but  <code>composer install</code> gets me nowhere, yielding:</p>
  
  <pre><code>Loading composer repositories with package information
  [Composer\Downloader\TransportException]                                                                             
  The "https://packagist.org/packages.json" file could not be downloaded: failed to open stream: Connection timed out 
  </code></pre>
  
  <p>Similarly, <code>composer diag</code> displays the following:</p>
  
  <pre><code>Checking composer.json: OK
  Checking platform settings: OK
  Checking git settings: OK
  Checking http connectivity: FAIL
  
  [Composer\Downloader\TransportException] The "//packagist.org/packages.json" file could not be downloaded: failed to open stream: Connection timed out
  
  Checking github.com rate limit: OK
  Checking disk free space: OK
  Checking composer version:
  [Composer\Downloader\TransportException]                                                                         
    The "//getcomposer.org/version" file could not be downloaded: failed to open stream: Connection timed out 
  </code></pre>
  
  <p>I've done searches on this error and have turned up discussions of how to get around a proxy. But according to the sysadmin, my IP has complete access, with no firewall or proxy blocking me. </p>
  
  <p>How do I begin to troubleshoot this?</p>
  
  <p><em>edit to add traceroute results per Sven's suggestion</em></p>
  
  <pre><code>traceroute to packagist.org (87.98.253.214), 30 hops max, 40 byte packets
  
  1  a9.39.5646.static.theplanet.com (70.86.57.169)  1.258 ms  1.532 ms  1.760 ms
  2  po202.dsr01.dllstx2.networklayer.com (70.87.254.145)  0.540 ms  0.579 ms  0.689 ms
  3  po21.dsr01.dllstx3.networklayer.com (70.87.255.65)  0.574 ms  0.676 ms  0.796 ms
  4  ae17.bbr02.eq01.dal03.networklayer.com (173.192.18.230)  0.406 ms  0.410 ms  0.404 ms
  5  * eqx.dal.ovh.net (206.223.118.119)  0.508 ms ae7.bbr01.eq01.dal03.networklayer.com (173.192.18.208)  0.401 ms
  6  * dal-1-6k.tx.us (178.32.135.174)  0.559 ms *
  7  nwk-1-6k.nj.us (178.32.135.222)  38.725 ms * *
  8  nwk-1-6k.nj.us (178.32.135.222)  38.690 ms  38.680 ms  38.773 ms
  9  * gra-g1-a9.fr.eu (37.187.36.211)  115.493 ms *
  10  gra-3a-a9.fr.eu (37.187.231.86)  113.173 ms gra-g1-a9.fr.eu (37.187.36.211)  113.189 ms  113.294 ms
  11  gra-3a-a9.fr.eu (37.187.231.86)  113.022 ms  111.916 ms *
  12  * * *
  13  * * *
  etc until
  30  * * *
  </code></pre>