Example of google OAuth2

set key $googleApplicationKey 
set secret $googleApplicationSecret
package require http

# Google APIs require https
package require http
package require tls
http::register https 443 ::tls::socket 
# Listen for an OAuth2 callback

 proc accept {chan addr port} {           ;# Make a proc to accept connections
     puts "Google says [gets $chan]" ;# Receive a string
     puts $chan goodbye                   ;# Send a string
     close $chan                          ;# Close the socket (automatically flushes)
 }                                        ;#


 proc start {cmd} {
   exec {*}[auto_execok start] "" $cmd
 }

 socket -server accept 12345              ;# Create a server socket


set endpoint https://accounts.google.com/o/oauth2/v2/auth

set params [list response_type code]
lappend params client_id $key
lappend params redirect_uri http://127.0.0.1:12345
lappend params scope profile
lappend params state "somerandomstringyoushouldcheckonreturntoprevent MIM attacks"

set result [http::geturl $endpoint -query [http::formatQuery {*}$params]]
upvar #0 $result state
puts "Copy this URL to your browser: [dict get $state(meta) Location]"