Updated 2016-02-14 13:24:13 by mel

Reading about HTML5 Websocket I noticed there was a Websocket Library in Tcllib. Reading the man page it could be used on existing webservers. Searching the wiki there was no information on using it with TclHttpd so I thought I would give it a try. Below are my efforts. I have created a Starkit with a demo which is available from [1]. (Right click on the link and select "Save target as...")

It works with the Tclkit 8.5.15 from Roy Keenes site but for some reason does not work with the Tclkit 8.6.1?

Point your browser to and click on the Websocket Test link on the home page.
# I made a few modifications to the Websocket library to make it work with Tclhttpd.
#       1. In the procedure ::websocket::test changed the following line from
#          [string equal -nocase $v "upgrade"] } {
#          to
#          [string compare -nocase $v "*upgrade*"] } {
#          Most browsers send the header "Connection: Upgrade" but Firefox sends
#          "Connection: keep-alive, Upgrade"
#       2. In the procedure ::websocket::takeover changed the following line from
#          fconfigure $sock -translation binary -blocking on
#          to
#          fconfigure $sock -translation binary -blocking off
#       So make the above modifications and then save the following to
#       websocket-echo.tcl and drop in the custom directory.

Url_PrefixInstall /sample [list ::sample::domain /sample]

        package require websocket

namespace eval ::sample {
         # ensure ::sample namespace exists

proc ::sample::domain {prefix sock suffix} {
        upvar #0 Httpd$sock data

# To get started register the socket as a websocket server.

        ::websocket::server $sock

# The callback procedure when a message/data is present.

        ::websocket::live $sock /sample ::sample::Echo

# Test the Http headers via data(headerlist) to see if it is a websocket request.

        set wstest [::websocket::test $sock $sock /sample $data(headerlist) $data(query)]

# If ::websocket::test returns 1 it's a valid websocket request so suspend the Http request
# in TclHttpd. Let the websocket library return the correct Http headers via the
# ::websocket::upgrade and take control.

        if {$wstest == 1} {
            Httpd_Suspend $sock 0
            ::websocket::upgrade $sock
        } else {
            Httpd_ReturnData $sock text/html "Not a valid Websocket connection!"

# ::sample::Echo --
#       This procedure is called when the server
#       can read data from the client
# Arguments: appended to the callback procedure by the Websocket library.
#       sock    The socket connection to the client
#       type    Type of message either:
#               request (initial connection generated by the websocket library.)
#               close
#               disconnect
#               binary
#               text
#       msg     message or data

proc ::sample::Echo {sock type msg} {

# Uncomment the following line to view what's being sent from the client.

#puts "Echo sock=$sock type=$type msg=$msg"

# All we want to do is echo back what was sent (thought I would append
# my own message ;-))

          switch $type {
                request {return }
                close { return }
                disconnect { return }
                binary { return }
                text {
                      ::websocket::send $sock text "$msg on the TclHttpd Web Server"

EF I've just published a change to the implementation to cover your problems with Firefox. I also made a number of changes a while ago to arrange for the library to work on the 8.6, but maybe I've missed something. What happens in the 8.6.1. kit? As for the blocking on/off change, let me figure out if that break things out elsewhere in the library, but if not, this is probably a good idea.

Jeff Smith The issue with the tclkit 8.6.1 is not a WebSocket Library issue. It happens when starting a generic tclhttpd3.5.1.kit with tclkit 8.6.1 from Roy's site. I'll investigate more and start a new wiki page if needed. Just thought I would mention it incase others were testing.

mel - 2016-02-14 13:24:13

I am trying to use websockets in my apache tcl code (not TCLHTTPD) and I have no idea how to get rid of vwait in my code to listen to websocket messages.

Can anyone please help ???

Examples work, but with vwait forever which makes my website in operaable

thank you