vncs, vncv – remote frame buffer server and viewer for Virtual Network Computing (VNC)

vncs [ –v ] [ –c cert ] [ –d :display ] [ –g widthxheight ] [ –p pixfmt ] [ –x net ] [ cmd [ args ] ]

vncs –k :display [ –x net ]

vncv [ –cstv ] [ –e encodings ] [ –k keypattern ] host[:n]

VNC is a lightweight protocol for accessing graphical applications remotely. The protocol allows one or more clients to connect to a server. While connected, clients display the frame buffer presented by the server and can send mouse events, keyboard events, and exchange snarf buffers. The server persists across viewer sessions, so that the virtual application can be accessed from various locations as its owner moves around.

VNC displays have names of the form host:n, where host is the machine's network name and n is a small integer identifier; display n is served on TCP port 5900+n.

Vncs starts a new virtual frame buffer in memory, simulating a Plan 9 terminal running cmd args, by default an interactive shell. As viewers connect, each is authenticated using a (rather breakable) challenge–response protocol using the user's Inferno/POP password.

The options are:
c cert   start TLS on each viewer connection using the certificate in the file cert. The corresponding private key must be loaded into the server's factotum(4). When serving TLS connections, the base port is 35729 rather than 5900.
d :n    run on display n ; without this option, the server searches for an unused display.
g widthxheight
set the virtual frame buffer to be widthxheight (default 1024x768) pixels.
p pixfmtset the virtual frame buffer's internal pixel format to pixfmt (default r5g6b5).
v       print verbose output to standard error.
x net    announce on an alternate network interface. Because of the weak authentication protocol and default lack of encryption, this option must be accompanied by –c.

The command vncs –k :n kills the VNC server running on display n.

Vncv provides access to remote display host:n. It resizes its window to be the smaller of the remote frame buffer size and the local screen.

The options are:
c    when connecting to 8–bit displays, request r4g4b4 pixels rather than r3g3b2 pixels. This takes up more bandwidth but usually gives significantly better matching to the Plan 9 color map.
e encodings
set the ordered list of allowed frame buffer update encodings. The default (and full) set is copyrect corre hextile rre raw. The encodings should be given as a single space–separated argument (quoted when using the shell).
k keypattern
add keypattern to the pattern used to select a key from factotum(4).
s    share the display with extant viewers; by default extant viewers are closed when a new viewer connects.
t    start TLS on the connection.
v    print verbose output to standard error.

The VNC protocol represents keyboard input as key up/down events. Plan 9 does not expose the state of the Ctl and Shift keys except as it can be inferred from receipt of control or shifted characters. It does not expose the state of the Alt key at all, since the Alt key is used to compose Unicode characters (see keyboard(6)). Vncv correctly handles the sending of control and shifted characters. To support systems that use key sequences like Alt–X (or worse, Alt–mouse–click), typing the Plan 9 compose sequences Alt Z A (for Alt), Alt Z C (for Ctrl), and Alt Z S (for Shift) will send a ``key down'' message for the given key. A corresponding ``key up'' message will be sent after the next key is pressed, or when the sequence is retyped, whichever happens first.



If the remote frame buffer is larger than the local screen, only the upper left corner can be accessed.

Vncv does no verification of the TLS certificate presented by the server.

Vncv supports only version 3.3 of the RFB protocol.

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