Accessing a MySQL database in R (RStudio) after tunneling via SSH - mysql

Question

I have the following problem.
Background:
I want to connect to a MySQL database and download tables into R.
The database (the MySQL prompt) can only be accessed via SSH tunnel to another server.
I am using Mac OSX El Capitan on a MacBook Pro (2015).
Problem:
From the 'terminal', I can easily SSH to the server, and thereon enter the MySQL prompt and run the queries I need.
I cannot, however, perform the latter tasks from within RStudio.
The code I tried is:
> system('ssh -f <server_user>#<server_ip> -N sleep 20')
> db <- dbConnect(MySQL(), host="hostname", user="username", pwd="password", dbname="databasename", port=3306)
> sql1 <- paste("SELECT * FROM databasename.tablename", sep="")
> results <- dbGetQuery(con, sql1)
> dbDisconnect(con)
While I can see from ps -A | grep ssh that the ssh process is running (for the 20 seconds I want it to), and in R the command executed normally (not waiting for more input), I cannot connect to the relevant database. The error message was something to effect of "could not connect", and RStudio hangs for at least a minute before the error appears.
The questions:
How does one
(1) Use SSH in conjunction with
(2) MySQL on the remote server to
(3) load tables directly into an R data frame?
Thanks.

Answer 1

You should use something which is called port forwarding. Some details are here (https://help.ubuntu.com/community/SSH/OpenSSH/PortForwarding)
For example, say you wanted to connect from your laptop to http://www.ubuntuforums.org using an SSH tunnel. You would use source port number 8080 (the alternate http port), destination port 80 (the http port), and destination server www.ubuntuforums.org. :
ssh -L 8080:www.ubuntuforums.org:80 <host>
Where <host> should be replaced by the name of your laptop.
This is done for whole computer so you dont need to do this from r studio.
Offcourse you need to forward your port to 3036. But you need special privilige on the server. Because on most hosting you can only connect from localhost (for example from php)