▼ |  | Web Server: HTTP Server

1 | Dispatching Server
2 | Dispatchers
3 | Launching Servers
4 | Web Servers
5 | Internal APIs
6 | Troubleshooting and Tips
| Index

► | 4 | Web Servers

4.1 | Server Units
4.2 | Configuration Units
4.3 | Configuration Table
4.4 | Configuration Table Structure
4.5 | Standard Responders

On this page:

4.1`` Server Units
4.1.1`` Signature
web-server^
serve
serve-ports
4.1.2`` Unit
web-server@
4.2`` Configuration Units
4.2.1`` Signature
web-config^
max-waiting
virtual-hosts
initial-connection-timeout
port
listen-ip
make-servlet-namespace
4.2.2`` Unit
configuration-table->web-config@
configuration-table-sexpr->web-config@
4.3`` Configuration Table
default-configuration-table-path
configuration-table-sexpr?
sexpr->configuration-table
configuration-table->sexpr
read-configuration-table
write-configuration-table
4.4`` Configuration Table Structure
configuration-table
host-table
host
responders
messages
timeouts
paths
4.5`` Standard Responders
file-response
servlet-loading-responder
gen-servlet-not-found
servlet-error-responder
gen-servlet-responder
gen-servlets-refreshed
gen-passwords-refreshed
gen-authentication-responder
gen-protocol-responder
gen-file-not-found-responder
gen-collect-garbage-responder

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### 4`` Web Servers

A Web server is a unit with the web-server^ signature. The most common way to construct one is to provide a web-config^ unit to the web-server@ unit. The most common way to construct a web-config^ unit is to use configuration-table->web-config@ to produce one from a configuration table file, such as the one that is shipped with Racket in default-configuration-table-path.

#### 4.1`` Server Units

(require web-server/web-server-sig)

> > signature

> > web-server^ : signature

> > > procedure

> > > (serve) → (-> void)

> Runs the server and returns a procedure that shuts down the server.

> > > procedure

> > > (serve-ports ip op) → void

> > ip : input-port?
> > op : output-port?

> Serves a single connection represented by the ports ip and op.

(require web-server/web-server-unit)

> > value

> > web-server@

> > :

> > (unit/c (web-config^ tcp^)
> > (web-server^))

Uses the web-config^ to construct a dispatcher/c function that sets up one virtual host dispatcher, for each virtual host in the web-config^, that sequences the following operations:

- Logs the incoming request with the given format to the given file

- Performs HTTP Basic Authentication with the given password file

- Allows the "/conf/refresh-passwords" URL to refresh the password file.

- Allows the "/conf/collect-garbage" URL to call the garbage collector.

- Allows the "/conf/refresh-servlets" URL to refresh the servlets cache.

- Executes servlets mapping URLs to the given servlet root directory under htdocs.

- Serves files under the "/" URL in the given htdocs directory.

Using this dispatcher/c, it loads a dispatching server that provides serve and serve-ports functions that operate as expected.

#### 4.2`` Configuration Units

(require web-server/web-config-sig)

> > signature

> > web-config^ : signature

Provides contains the following identifiers.

> > > value

> > > max-waiting : integer?

> Passed to tcp-accept.

> > > value

> > > virtual-hosts : (string? . -> . host?)

> Contains the configuration of individual virtual hosts.

> > > value

> > > initial-connection-timeout : integer?

> Specifies the initial timeout given to a connection.

> > > value

> > > port : port-number?

> Specifies the port to serve HTTP on.

> > > value

> > > listen-ip : (or/c false/c string?)

> Passed to tcp-listen.

> > > value

> > > make-servlet-namespace : make-servlet-namespace/c

> Passed to servlets:make through make-default-path->servlet.

(require web-server/web-config-unit)

> > procedure

> > (configuration-table->web-config@ |
> > |  | path |
> > | [ | #:port port |
> > |  | #:listen-ip listen-ip |
> > |  | #:make-servlet-namespace make-servlet-namespace]) |

> → (unit/c (import) (export web-config^))
> path : path-string?
> port : (or/c false/c port-number?) = #f
> listen-ip : (or/c false/c string?) = #f

> | make-servlet-namespace |  | : |  | make-servlet-namespace/c
> |  |  | = |  | (make-make-servlet-namespace)

Reads the S-expression at path and calls configuration-table-sexpr->web-config@ appropriately.

> > procedure

> > (configuration-table-sexpr->web-config@ |
> > |  | sexpr |
> > | [ | #:web-server-root web-server-root |
> > |  | #:port port |
> > |  | #:listen-ip listen-ip |
> > |  | #:make-servlet-namespace make-servlet-namespace]) |

> → (unit/c (import) (export web-config^))
> sexpr : list?

> | web-server-root |  | : |  | path-string?
> |  |  | = |  | (directory-part default-configuration-table-path)

> port : (or/c false/c port-number?) = #f
> listen-ip : (or/c false/c string?) = #f

> | make-servlet-namespace |  | : |  | make-servlet-namespace/c
> |  |  | = |  | (make-make-servlet-namespace)

Parses sexpr as a configuration-table and constructs a web-config^ unit.

#### 4.3`` Configuration Table

(require web-server/configuration/configuration-table)

This module provides functions for reading, writing, parsing, and printing configuration-table structures.

> > value

> > default-configuration-table-path : path?

The default configuration table S-expression file.

> > value

> > configuration-table-sexpr? : (any . -> . boolean?)

Equivalent to list?.

> > procedure

> > (sexpr->configuration-table sexpr) → configuration-table?

> sexpr : configuration-table-sexpr?

This function converts a configuration-table from an S-expression.

> > procedure

> > (configuration-table->sexpr ctable)

> → configuration-table-sexpr?
> ctable : configuration-table?

This function converts a configuration-table to an S-expression.
The configuration table format is:

> `((port ,integer?)
> (max-waiting ,exact-integer?)
> (initial-connection-timeout ,integer?)
> (default-host-table
> ,host-table-sexpr?)
> (virtual-host-table
> (list ,symbol? ,host-table-sexpr?)
> ...))

where a host-table-sexpr is:

> `(host-table
> (default-indices ,string? ...)
> (log-format ,symbol?)
> (messages
> (servlet-message ,path-string?)
> (authentication-message ,path-string?)
> (servlets-refreshed ,path-string?)
> (passwords-refreshed ,path-string?)
> (file-not-found-message ,path-string?)
> (protocol-message ,path-string?)
> (collect-garbage ,path-string?))
> (timeouts
> (default-servlet-timeout ,integer?)
> (password-connection-timeout ,integer?)
> (servlet-connection-timeout ,integer?)
> (file-per-byte-connection-timeout ,integer?)
> (file-base-connection-timeout ,integer))
> (paths
> (configuration-root ,path-string?)
> (host-root ,path-string?)
> (log-file-path ,path-string?)
> (file-root ,path-string?)
> (servlet-root ,path-string?)
> (mime-types ,path-string?)
> (password-authentication ,path-string?)))

In this syntax, the 'messages paths are relative to the 'configuration-root directory. All the paths in 'paths except for 'servlet-root are relative to 'host-root (other than 'host-root obviously.) The 'servlet-root path is relative to 'file-root.
Allowable 'log-formats are those accepted by log-format->format.
Note: You almost always want to leave everything in the 'paths section the default except the 'host-root.

> > procedure

> > (read-configuration-table path) → configuration-table?

> path : path-string?

This function reads a configuration-table from path.

> > procedure

> > (write-configuration-table ctable path) → void

> ctable : configuration-table?
> path : path-string?

This function writes a configuration-table to path.

#### 4.4`` Configuration Table Structure

(require web-server/configuration/configuration-table-structs)

This module provides the following structures that represent a standard configuration (see Server Units) of the Web Server . The contracts on this structure influence the valid types of values in the configuration table S-expression file format described in Configuration Table.

> > struct

> > (struct |  | configuration-table | ( | port
> > |  |  |  | max-waiting
> > |  |  |  | initial-connection-timeout
> > |  |  |  | default-host
> > |  |  |  | virtual-hosts)
> > |  | #:extra-constructor-name make-configuration-table)

> port : port-number?
> max-waiting : natural-number/c
> initial-connection-timeout : natural-number/c
> default-host : host-table?
> virtual-hosts : (listof (cons/c string? host-table?))

> > struct

> > (struct |  | host-table (indices log-format messages timeouts paths)
> > |  | #:extra-constructor-name make-host-table)

> indices : (listof string?)
> log-format : symbol?
> messages : messages?
> timeouts : timeouts?
> paths : paths?

> > struct

> > (struct |  | host | ( | indices
> > |  |  |  | log-format
> > |  |  |  | log-path
> > |  |  |  | passwords
> > |  |  |  | responders
> > |  |  |  | timeouts
> > |  |  |  | paths)
> > |  | #:extra-constructor-name make-host)

> indices : (listof string?)
> log-format : symbol?
> log-path : (or/c false/c path-string?)
> passwords : (or/c false/c path-string?)
> responders : responders?
> timeouts : timeouts?
> paths : paths?

> > struct

> > (struct |  | responders | ( | servlet
> > |  |  |  | servlet-loading
> > |  |  |  | authentication
> > |  |  |  | servlets-refreshed
> > |  |  |  | passwords-refreshed
> > |  |  |  | file-not-found
> > |  |  |  | protocol
> > |  |  |  | collect-garbage)
> > |  | #:extra-constructor-name make-responders)

> servlet : (url? any/c . -> . response?)
> servlet-loading : (url? any/c . -> . response?)
> authentication : (url? (cons/c symbol? string?) . -> . response?)
> servlets-refreshed : (-> response?)
> passwords-refreshed : (-> response?)
> file-not-found : (request? . -> . response?)
> protocol : (url? . -> . response?)
> collect-garbage : (-> response?)

> > struct

> > (struct |  | messages | ( | servlet
> > |  |  |  | authentication
> > |  |  |  | servlets-refreshed
> > |  |  |  | passwords-refreshed
> > |  |  |  | file-not-found
> > |  |  |  | protocol
> > |  |  |  | collect-garbage)
> > |  | #:extra-constructor-name make-messages)

> servlet : string?
> authentication : string?
> servlets-refreshed : string?
> passwords-refreshed : string?
> file-not-found : string?
> protocol : string?
> collect-garbage : string?

> > struct

> > (struct |  | timeouts | ( | default-servlet
> > |  |  |  | password
> > |  |  |  | servlet-connection
> > |  |  |  | file-per-byte
> > |  |  |  | file-base)
> > |  | #:extra-constructor-name make-timeouts)

> default-servlet : number?
> password : number?
> servlet-connection : number?
> file-per-byte : number?
> file-base : number?

> > struct

> > (struct |  | paths | ( | conf
> > |  |  |  | host-base
> > |  |  |  | log
> > |  |  |  | htdocs
> > |  |  |  | servlet
> > |  |  |  | mime-types
> > |  |  |  | passwords)
> > |  | #:extra-constructor-name make-paths)

> conf : (or/c false/c path-string?)
> host-base : (or/c false/c path-string?)
> log : (or/c false/c path-string?)
> htdocs : (or/c false/c path-string?)
> servlet : (or/c false/c path-string?)
> mime-types : (or/c false/c path-string?)
> passwords : (or/c false/c path-string?)

#### 4.5`` Standard Responders

(require web-server/configuration/responders)

This module provides some functions that help constructing HTTP responders. These functions are used by the default dispatcher constructor (see Server Units) to turn the paths given in the configuration-table into responders for the associated circumstance.

> > procedure

> > (file-response |  | http-code |  |  |  |
> > |  | short-version |  |  |  |
> > |  | text-file |  |  |  |
> > |  | header ...) |  | → |  | response?

> http-code : natural-number/c
> short-version : string?
> text-file : string?
> header : header?

Generates a response? with the given http-code and short-version as the corresponding fields; with the content of the text-file as the body; and, with the headers as, you guessed it, headers.
This does not cause redirects to a well-known URL, such as "conf/not-found.html", but rather use the contents of "not-found.html" (for example) as its contents. Therefore, any relative URLs in text-file are relative to whatever URL file-response is used to respond to. Thus, you should probably use absolute URLs in these files.

> > procedure

> > (servlet-loading-responder url exn) → response?

> url : url?
> exn : exn?

Gives exn to the current-error-handler and response with a stack trace and a "Servlet didn’t load" message.

> > procedure

> > (gen-servlet-not-found file) → ((url url?) . -> . response?)

> file : path-string?

Returns a function that generates a standard "Servlet not found." error with content from file.

> > procedure

> > (servlet-error-responder url exn) → response?

> url : url?
> exn : exn?

Gives exn to the current-error-handler and response with a stack trace and a "Servlet error" message.

> > procedure

> > (gen-servlet-responder file)

> → ((url url?) (exn any/c) . -> . response?)
> file : path-string?

Prints the exn to standard output and responds with a "Servlet error." message with content from file.

> > procedure

> > (gen-servlets-refreshed file) → (-> response?)

> file : path-string?

Returns a function that generates a standard "Servlet cache refreshed." message with content from file.

> > procedure

> > (gen-passwords-refreshed file) → (-> response?)

> file : path-string?

Returns a function that generates a standard "Passwords refreshed." message with content from file.

> > procedure

> > (gen-authentication-responder file)

> → ((url url?) (header header?) . -> . response?)
> file : path-string?

Returns a function that generates an authentication failure error with content from file and header as the HTTP header.

> > procedure

> > (gen-protocol-responder file) → ((url url?) . -> . response?)

> file : path-string?

Returns a function that generates a "Malformed request" error with content from file.

> > procedure

> > (gen-file-not-found-responder file)

> → ((req request?) . -> . response?)
> file : path-string?

Returns a function that generates a standard "File not found" error with content from file.

> > procedure

> > (gen-collect-garbage-responder file) → (-> response?)

> file : path-string?

Returns a function that generates a standard "Garbage collection run" message with content from file.
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