I have just started at University and the current setup is an Ethernet connection which comes out of the wall and goes into the back of my computer. I then have an Xbox 360 which is not currently connected to the Internet (Xbox Live). Unfortunately, since the source cable from the wall is an Ethernet cable, it means that I cannot run my Router which requires the standard RJ45 connection into the "Internet" socket. I have been told by my accommodation that it is completely possible to use the Xbox 360 and a computer at the same time on the Internet using the provided connection. However, I cannot see how I can split the Ethernet to run both my computer AND XBOX 360 without the use of a specific type of router, unless there is a product which supports 3+ Ethernet connections and uses one as a source??
I'm not sure if I understand you correctly.
If you get a router nowadays it will have 5 ports for a rj45 in the back.
One for uplink – internet connection from the wall and the rest are for computers and XBOXs or shares.
You might not have the bandwidth needed since you're at school.

More than likely you will have to purchase a router that supports those plug ins to allow more devices such as your xbox to connect to the internet . The more hassle free way is to just get a wireless router . I am pretty sure that it does support wireless connectivity . But don't hold me to that .
References :
I'm not sure if I understand you correctly.
If you get a router nowadays it will have 5 ports for a rj45 in the back.
One for uplink – internet connection from the wall and the rest are for computers and xboxs or shares.
You might not have the bandwidth needed since you're at school.
References :