Learn Remote Desktop - VNC Clients & the First Connection

#Introduction

The last two episodes focused on the server: x11vnc and TigerVNC are now running on your machine. Episode 6 shifts the perspective to the client side. A great server is worthless without a viewer that can connect — and most remote desktop failures actually happen at the first connection stage.

This episode introduces you to the main viewers (TigerVNC Viewer, Remmina, Vinagre, RealVNC), explains the host:display versus host:port address format that often confuses beginners, then walks you through making the first connection and diagnosing failures systematically.

#VNC Viewers: Options and Advantages

#Four Viewers Worth Knowing

Each viewer has its own character. You should master at least two:

• TigerVNC Viewer (vncviewer) — a lightweight command-line viewer, available on all platforms, and well suited for scripts and tunnels. The focus of this episode.
• Remmina — a versatile GUI viewer from the GTK world; supports VNC, RDP, SSH, and SPICE in one application. A favorite for daily Linux use.
• Vinagre — GNOME's simple built-in viewer, good for quick connections without complex configuration.
• RealVNC — the viewer from the commercial vendor; often used in enterprise environments that already run RealVNC Server.

Install any viewers you don't have yet:

sudo apt install tigervnc-viewer remmina vinagre

The apt install tigervnc-viewer remmina vinagre command installs three viewers at once so you can try each one and pick your favorite.

#Understanding the Address Format

#host:display versus host:port

The number one source of confusion for beginners is the two ways of writing a VNC address. Both are valid and point to the same place:

• Display format: host:1 — the server computes 5900 + display, so this points to port 5901.
• Port format: host:5901 — points directly to the explicit port.

server:1        ==  server:5901
192.168.1.20:2  ==  192.168.1.20:5902

The formula is simple: port equals 5900 plus the display number. If the server uses display :1, the address can be written as host:1 or host:5901 — they're identical.

#The First Connection

#Using vncviewer

Now let's connect to the server you created in episode 5:

vncviewer localhost:1

The vncviewer localhost:1 command connects to the VNC server on localhost display :1. You'll be asked for the password (created with vncpasswd), then the Xfce or KDE desktop configured in xstartup will appear.

#Connecting to Another Machine on the Network

For a server on another machine, replace localhost with its IP address:

vncviewer 192.168.1.10:5901

The vncviewer 192.168.1.10:5901 command connects to IP 192.168.1.10 on port 5901. Change it to match your server's address — and make sure the server firewall allows that port in (episodes 0 and 12).

#Diagnosing Failed Connections

#Sequential Checks

When a connection fails, don't guess. Run checks in sequence, from the network layer to the server layer:

ping -c 3 192.168.1.10
nc -zv 192.168.1.10 5901

If ping fails, the problem is the network. If ping succeeds but nc -zv fails, the port isn't open — check the VNC server and firewall. The nc -zv command tells you whether the port accepts TCP connections, before you bother checking the password.

#Common Errors and Their Fixes

Here's a map of the most frequent errors:

• "Connection refused" — the VNC server isn't running or the port is wrong. Run vncserver -list on the server.
• "Authentication failed" — wrong password, or the passwd file doesn't match the server. Recreate it with vncpasswd.
• Timeout / hanging — the firewall is blocking the port. Check ss -tulpn and the firewall rules.
• Gray screen — xstartup is problematic or the DE isn't installed. Check the logs in ~/.vnc/.

vncserver -list
ss -tulpn | grep 590

vncserver -list shows the active sessions; ss -tulpn | grep 590 confirms the port is really listening. These two commands answer 80 percent of "why can't I connect" questions.

#Conclusion

Episode 6 completed the first bridge between server and client: you got to know the four main viewers, understood the equivalent host:display and host:port address formats, made your first connection to display :1, and performed sequential diagnosis when the connection fails.

Key takeaways:

• host:display and host:port are equivalent: :1 means port 5901.
• TigerVNC Viewer for the command line; Remmina for daily GUI use.
• vncviewer localhost:1 for local testing; replace with the IP for remote use.
• nc -zv separates network problems from authentication problems.
• A gray screen almost always comes from ~/.vnc/xstartup.

In the next episode, episode 7, we level up to VNC configuration and customization — preparing ~/.vnc/xstartup for GNOME, Xfce, and KDE, setting geometry and depth, running several servers at once with separate users and displays, and closing sessions with vncserver -kill. See you in the next episode!