It looks like the target machine has a webserver on it, so open your webbrowser and try to acces the file via the following url...
"http://10.0.0.1/file.txt"
If that doesn't work, move the file to either the html or htdocs directory under www (whichever is there) on the target machine. It all depends on where the index.html for that server resides. (What is the url you enter to acces that machine thru your browser?)
When you can see the text file in your browser, you've found the path you need for your fopen.
AMD is a program to run on Unix or Linux that will let you access other computers thru relative links. Most of the time the link you would use looks like the following... "/net/remotecomputername/remotedirectory/filename", as if the remote computer were mapped as a network drive or as if it were a local directory. You can get AMD (the download file is called am-utils...) from
http://rpmfind.net/linux/rpm2html/search.php?query=am-utils amopng other places.
If you're not using Linux or Unix, then I'm not sure what you could use for AMD-like network access.