HTTPS or SSH for server-server communication

I have two servers. I wish to send some data ( was doing it with HTTP GET till now ) to a php file residing on the server and get some output from it.

Of late, I saw the requests per second went up to 50 and Apache served HTTP 500 error for some of those. This server has 512 MB RAM and the script, in php-cli mode, usu开发者_开发百科ally eats up around 10 MB of memory.

I wish, if it were to reduce the load on server, to use SSH instead of HTTPS. Will it reduce the memory usage on this server (minus what the script itself needs)? Or will too many SSH connections still cause hindrance?

Note - I do not have HTTPS setup right now. But planning to switch over to it. And just then, this issue cropped up.

SSH will not speed up your program. What you can do, is to create your own server on the destination server (which will receive data). The web server do much more than just receive data, like interpret HTTP headers and route your requests to files. Your own server can do the same job in a much lighter way.

http://br.php.net/manual/en/sockets.examples.php has an example of how to do this.

I would use normal HTTP, but encrypt the data sent.

How big is the data you're wanting to transfer? Depending on the size SSH (in particular, SFTP) might very well be better. I say that because... well, when was the last time you tried to upload a 10MB file via a webpage and succeeded? Uploading small files works for HTTP but, at the end of the day, it's not a file transfer protocol.

My recommendation would be to use phpseclib, a pure PHP SFTP implementation. Upload a file via SFTP and then run a PHP script on that file via SSH.