unreliably reading external files

[zimma]

I'm having a problem with a website as it seems to be unreliable at reading external files.

 

Classic examples include accessing files payment notification from online payment systems but also simply reading xml files.

 

Sometimes they work, sometimes they don't. When it's not working it's usually for a period of time. For example there may be a time for two hours when no payments are processed properly and no xml files can be read and then it will be fine again.

 

Is there a limit to how much the server can open from external sources?

Is there any way of setting it up so that it's more reliable?

I'm using a virtual server. Do I need to upgrade?

 

I'm using the following functions to access external files and these all have problems occasionally but not all the time (which suggests the configuration of the server is fine)

 

fsockopen

fopen

simplexml_load_file

copy

 

Any help would be greatly appreciated.

 

Many thanks.