Linux Remote Access [Basic Guide]

Remote access to Linux in the graphical environment can be done through tools and protocols, such as:

X11

The X11 protocol is the form of native communication between the X.Org Server and X applications.

It uses TCP as a transport protocol, typically between port 6000 and 6063, starting at port 6000, added to the Display number.

Access control to the protocol can take place through a firewall, restricting access to ports 6000-6063 Only the hosts allowed, in addition to the control in the application with the xhost command.

XDMCP

The architecture of X.Org is so modular that it allows the Window Manager to run on the same host as the X Server, or remotely on another host.

The XDMCP protocol (acronym for X D Display M Manager C Control P Protocol) was created to format the communication between the X Server and the X Window Display Manager.

It uses the UDP transport protocol on port 177 and is insecure as it doesn’t encrypt your traffic.

XDMCP is analogous to telnet and therefore shares the same security problems, allowing, for example through a wireless network, anyone to “listen” to traffic and easily record keystrokes.

VNC

VNC is a set of applications that can be used for remote access to the graphical environment. It consists of a server, which listens on TCP port 5900, and a Client VNC, capable of connecting it to a server running the VNC Server.

It is widely used for remote access, since it is multiplatform, allowing remote access on Windows, Mac OS, Linux, AIX, HP-UX and Solaris.

So versatile, the VNC client can run on the Java platform and Mobile as well as on Apple iPhone, iPod touch, iPad and also on Google Android devices.

Its authentication is simple, through a password configured on the VNC Server.

SPICE

SPICE (acronym for S Simple Protocol for I Independent Computing E Environments) is a remote display system created for virtual environments that allows viewing Desktop environment in a wide variety of architectures.

Of all the remote connection protocols, SPICE is the most powerful of them, as it provides a complete remote access solution to virtual machines that allows you to play videos, record audio, share USB devices and share folders without complications.

SPICE can be divided into 4 different components: protocol, client, server, and guest:

• The protocol is the communication specification for the three other components;
• a client is the remote viewer responsible for sending data and translating the data from the Virtual Machine (VM) so that you can interact with it;
• the SPICE server is the library used by the hypervisor (Operating System) Host), in order to share the Virtual Machine using the SPICE Protocol;
• The guest is all the software that must be run on the Virtual Machine in order to make SPICE fully functional, such as the QXL driver and SPICE VDAgent.

SPICE is specially designed to provide remote access to virtual machines with the experience of a local machine.

RDP

RDP (acronym for Remote Desktop Protocol) is a multi-channel protocol created by Microsoft for remote access to the Desktop.

RDP clients exist for most versions of Windows, and also for Linux.

The RDP server listens by default on TCP port 3389.

FreeRDP is an implementation of RDP under the terms of free software and is licensed under the Apache License. Following Microsoft’s Open Specifications, FreeRDP provides a client application for connections using the RDP protocol from Linux to Windows Servers.

The xrdp implementation also provides the server-side of RDP for Linux, accepting connections from a variety of clients such as FreeRDP, rdesktop, and the Microsoft Desktop Client.

NX

The NX created by NoMachine is another remote desktop sharing protocol. Its technology in version 3.5 was open source and available under the GNU GPL2 license. However, starting with version 4 it became proprietary and closed source.

This led to some open source variations being implemented, such as FreeNX and X2Go.

NX technology provides excellent response time, even on low bandwidth connections, and is faster than VNC-based products.

NX uses OpenSSH tunneling with traffic is encrypted, which is great for remote access via the Internet.

In addition, the NX supports multiple concurrent users, compresses X11 data, and employs the use of cache to provide an improved remote desktop experience.

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