ASP.NET Need to write a file on another server

here is my task,

 

i have two web application web1 web2 running on two IIS servers in different location..

 

im going to send a content from one web1 application, and it should open and write that content to already existing txt file in web2 server ...

 

web2 server returns "access denied" because of file permission. 

 

actully i dont which kind of file permission the file has in web2 server...

 

web2 application should write the content which is received from web1 application...

 

 

 by browsing i found using "chmod" can be used to chnage the file permission... 

 

here is one more doubt  .. if we are using "chmod" wheather we need admin username and password?? or no need, simply we can change the file permission???