Tcl Library Source Code

httpd - Tcl Web Server

[ Main Table Of Contents | Table Of Contents | Keyword Index | Categories | Modules | Applications ]

httpd(n) 4.3 tcllib "Tcl Web Server"


httpd - A TclOO and coroutine based web server


  • package require Tcl 8.6
  • package require httpd ?1.7?
  • package require uuid
  • package require clay
  • package require coroutine
  • package require fileutil
  • package require fileutil::magic::filetype
  • package require websocket
  • package require mime
  • package require cron
  • package require uri
  • package require Markdown


This module implements a web server, suitable for embedding in an application. The server is object oriented, and contains all of the fundamentals needed for a full service website.

Minimal Example

Starting a web service requires starting a class of type httpd::server, and providing that server with one or more URIs to service, and httpd::reply derived classes to generate them.

oo::class create ::reply.hello {
  method content {} {
    my puts "<HTML><HEAD><TITLE>IRM Dispatch Server</TITLE></HEAD><BODY>"
    my puts "<h1>Hello World!</h1>"
    my puts </BODY></HTML>
::httpd::server create HTTPD port 8015 myaddr doc_root ~/htdocs
HTTPD plugin dispatch httpd::server::dispatch
HTTPD uri add * /hello [list mixin reply.hello]

The bare module does have facilities to hose a files from a file system. Files that end in a .tml will be substituted in the style of Tclhttpd:

<!-- hello.tml -->
[my html_header {Hello World!}]
Your Server is running.
The time is now [clock format [clock seconds]]
[my html_footer]

A complete example of an httpd server is in the /examples directory of Tcllib. It also show how to dispatch URIs to other processes via SCGI and HTTP proxies.

cd ~/tcl/sandbox/tcllib
tclsh examples/httpd.tcl


Class httpd::mime


method ChannelCopy in out ?args?
method html_header ?title ? ?args?
method html_footer ?args?
method http_code_string code
method HttpHeaders sock ?debug ?
method HttpHeaders_Default
method HttpServerHeaders
method MimeParse mimetext

Converts a block of mime encoded text to a key/value list. If an exception is encountered, the method will generate its own call to the error method, and immediately invoke the output method to produce an error code and close the connection.

method Url_Decode data

De-httpizes a string.

method Url_PathCheck urlsuffix
method wait mode sock

Class httpd::reply

ancestors: httpd::mime

A class which shephards a request through the process of generating a reply. The socket associated with the reply is available at all times as the chan variable. The process of generating a reply begins with an httpd::server generating a http::class object, mixing in a set of behaviors and then invoking the reply object's dispatch method. In normal operations the dispatch method:

  1. Invokes the reset method for the object to populate default headers.

  2. Invokes the HttpHeaders method to stream the MIME headers out of the socket

  3. Invokes the request parse method to convert the stream of MIME headers into a dict that can be read via the request method.

  4. Stores the raw stream of MIME headers in the rawrequest variable of the object.

  5. Invokes the content method for the object, generating an call to the error method if an exception is raised.

  6. Invokes the output method for the object

Developers have the option of streaming output to a buffer via the puts method of the reply, or simply populating the reply_body variable of the object. The information returned by the content method is not interpreted in any way. If an exception is thrown (via the error command in Tcl, for example) the caller will auto-generate a 500 {Internal Error} message. A typical implementation of content look like:

 clay::define ::test::content.file {
 	superclass ::httpd::content.file
 	# Return a file
 	# Note: this is using the content.file mixin which looks for the reply_file variable
 	# and will auto-compute the Content-Type
 	method content {} {
 	  my reset
     set doc_root [my request get DOCUMENT_ROOT]
     my variable reply_file
     set reply_file [file join $doc_root index.html]
 clay::define ::test::content.time {
   # return the current system time
 	method content {} {
 		my variable reply_body
     my reply set Content-Type text/plain
 		set reply_body [clock seconds]
 clay::define ::test::content.echo {
 	method content {} {
 		my variable reply_body
     my reply set Content-Type [my request get CONTENT_TYPE]
 		set reply_body [my PostData [my request get CONTENT_LENGTH]]
 clay::define ::test::content.form_handler {
 	method content {} {
 	  set form [my FormData]
 	  my reply set Content-Type {text/html; charset=UTF-8}
     my puts [my html_header {My Dynamic Page}]
     my puts "<BODY>"
     my puts "You Sent<p>"
     my puts "<TABLE>"
     foreach {f v} $form {
       my puts "<TR><TH>$f</TH><TD><verbatim>$v</verbatim></TD>"
     my puts "</TABLE><p>"
     my puts "Send some info:<p>"
     my puts "<FORM action=/[my request get REQUEST_PATH] method POST>"
     my puts "<TABLE>"
     foreach field {name rank serial_number} {
       set line "<TR><TH>$field</TH><TD><input name=\"$field\" "
       if {[dict exists $form $field]} {
         append line " value=\"[dict get $form $field]\"""
       append line " /></TD></TR>"
       my puts $line
     my puts "</TABLE>"
     my puts [my html footer]


method constructor ServerObj ?args?
method destructor ?dictargs?

clean up on exit

method close

Close channels opened by this object

method Log_Dispatched

Record a dispatch event

method dispatch newsock datastate

Accept the handoff from the server object of the socket newsock and feed it the state datastate. Fields the datastate are looking for in particular are:

* mixin - A key/value list of slots and classes to be mixed into the object prior to invoking Dispatch.

* http - A key/value list of values to populate the object's request ensemble

All other fields are passed along to the clay structure of the object.

method Dispatch
method html_css
method html_header title ?args?
method html_footer ?args?
method error code ?msg ? ?errorInfo ?
method content

REPLACE ME: This method is the "meat" of your application. It writes to the result buffer via the "puts" method and can tweak the headers via "clay put header_reply"

method EncodeStatus status

Formulate a standard HTTP status header from he string provided.

method log type ?info ?
method CoroName
method DoOutput

Generates the the HTTP reply, streams that reply back across chan, and destroys the object.

method FormData

For GET requests, converts the QUERY_DATA header into a key/value list. For POST requests, reads the Post data and converts that information to a key/value list for application/x-www-form-urlencoded posts. For multipart posts, it composites all of the MIME headers of the post to a singular key/value list, and provides MIME_* information as computed by the mime package, including the MIME_TOKEN, which can be fed back into the mime package to read out the contents.

method PostData length

Stream length bytes from the chan socket, but only of the request is a POST or PUSH. Returns an empty string otherwise.

method Session_Load

Manage session data

method TransferComplete ?args?

Intended to be invoked from chan copy as a callback. This closes every channel fed to it on the command line, and then destroys the object.

     # Output the body
     chan configure $sock -translation binary -blocking 0 -buffering full -buffersize 4096
     chan configure $chan -translation binary -blocking 0 -buffering full -buffersize 4096
     if {$length} {
       # Send any POST/PUT/etc content
       chan copy $sock $chan -size $SIZE -command [info coroutine]
     catch {close $sock}
     chan flush $chan
method puts line

Appends the value of string to the end of reply_body, as well as a trailing newline character.

method RequestFind field
method request subcommand ?args?
method reply subcommand ?args?
method reset

Clear the contents of the reply_body variable, and reset all headers in the reply structure back to the defaults for this object.

method timeOutCheck

Called from the http::server object which spawned this reply. Checks to see if too much time has elapsed while waiting for data or generating a reply, and issues a timeout error to the request if it has, as well as destroy the object and close the chan socket.

method timestamp

Return the current system time in the format:

%a, %d %b %Y %T %Z

Class httpd::server

ancestors: httpd::mime


method constructor args ?port auto? ?myaddr ?string auto? ?name auto? ?doc_root ? ?reverse_dns 0? ?configuration_file ? ?protocol HTTP/1.1?
method destructor ?dictargs?
method connect sock ip port

Reply to an open socket. This method builds a coroutine to manage the remainder of the connection. The coroutine's operations are driven by the Connect method.

method ServerHeaders ip http_request mimetxt
method Connect uuid sock ip

This method reads HTTP headers, and then consults the dispatch method to determine if the request is valid, and/or what kind of reply to generate. Under normal cases, an object of class ::http::reply is created, and that class's dispatch method. This action passes control of the socket to the reply object. The reply object manages the rest of the transaction, including closing the socket.

method counter which

Increment an internal counter.

method CheckTimeout

Check open connections for a time out event.

method debug ?args?
method dispatch data

Given a key/value list of information, return a data structure describing how the server should reply.

method Dispatch_Default reply

Method dispatch method of last resort before returning a 404 NOT FOUND error. The default behavior is to look for a file in DOCUMENT_ROOT which matches the query.

method Dispatch_Local data

Method dispatch method invoked prior to invoking methods implemented by plugins. If this method returns a non-empty dictionary, that structure will be passed to the reply. The default is an empty implementation.

method Headers_Local varname

Introspect and possibly modify a data structure destined for a reply. This method is invoked before invoking Header methods implemented by plugins. The default implementation is empty.

method Headers_Process varname

Introspect and possibly modify a data structure destined for a reply. This method is built dynamically by the plugin method.

method HostName ipaddr

Convert an ip address to a host name. If the server/ reverse_dns flag is false, this method simply returns the IP address back. Internally, this method uses the dns module from tcllib.

method log ?args?

Log an event. The input for args is free form. This method is intended to be replaced by the user, and is a noop for a stock http::server object.

method plugin slot ?class ?

Incorporate behaviors from a plugin. This method dynamically rebuilds the Dispatch and Headers method. For every plugin, the server looks for the following entries in clay plugin/:

load - A script to invoke in the server's namespace during the plugin method invokation.

dispatch - A script to stitch into the server's Dispatch method.

headers - A script to stitch into the server's Headers method.

thread - A script to stitch into the server's Thread_start method.

method port_listening

Return the actual port that httpd is listening on.

method PrefixNormalize prefix

For the stock version, trim trailing /'s and *'s from a prefix. This method can be replaced by the end user to perform any other transformations needed for the application.

method source filename
method start

Open the socket listener.

method stop

Shut off the socket listener, and destroy any pending replies.

method SubObject {} db
method SubObject {} default
method template page

Return a template for the string page

method TemplateSearch page

Perform a search for the template that best matches page. This can include local file searches, in-memory structures, or even database lookups. The stock implementation simply looks for files with a .tml or .html extension in the ?doc_root? directory.

method Thread_start

Built by the plugin method. Called by the start method. Intended to allow plugins to spawn worker threads.

method Uuid_Generate

Generate a GUUID. Used to ensure every request has a unique ID. The default implementation is:

   return [::uuid::uuid generate]
method Validate_Connection sock ip

Given a socket and an ip address, return true if this connection should be terminated, or false if it should be allowed to continue. The stock implementation always returns 0. This is intended for applications to be able to implement black lists and/or provide security based on IP address.

Class httpd::server::dispatch

ancestors: httpd::server

Provide a backward compadible alias

Class httpd::content.file

Class to deliver Static content When utilized, this class is fed a local filename by the dispatcher


method FileName
method DirectoryListing local_file
method content
method Dispatch

Class httpd::protocol.scgi

Return data from an SCGI process


method EncodeStatus status

Class httpd::server.scgi

ancestors: httpd::server

Act as an SCGI Server


method debug ?args?
method Connect uuid sock ip

Class httpd::content.websocket

Upgrade a connection to a websocket

Class httpd::plugin

httpd plugin template

Class httpd::plugin.dict_dispatch

A rudimentary plugin that dispatches URLs from a dict data structure


method Dispatch_Dict data

Implementation of the dispatcher

method uri {} add vhosts patterns info
method uri {} direct vhosts patterns info body

Class httpd::plugin.local_memchan


method local_memchan command ?args?
method Connect_Local uuid sock ?args?

A modified connection method that passes simple GET request to an object and pulls data directly from the reply_body data variable in the object Needed because memchan is bidirectional, and we can't seem to communicate that the server is one side of the link and the reply is another


Sean Woods

Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category network of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.