Wt  4.0.2
Classes | Public Member Functions | Static Public Member Functions | Related Functions | List of all members
Wt::WServer Class Reference

A class encapsulating a web application server. More...

#include <Wt/WServer.h>


class  Exception
 Server Exception class. More...
class  SessionInfo
 Contains the information for one session. More...

Public Member Functions

WTCONNECTOR_API WServer (const std::string &wtApplicationPath=std::string(), const std::string &wtConfigurationFile=std::string())
 Creates a new server instance. More...
WTCONNECTOR_API WServer (int argc, char *argv[], const std::string &wtConfigurationFile=std::string())
 Creates a new server instance and configures it. More...
virtual WTCONNECTOR_API ~WServer ()
 Destructor. More...
WT_API void setIOService (WIOService &ioService)
 Sets the I/O service. More...
WT_API WIOServiceioService ()
 Returns the I/O service. More...
WTCONNECTOR_API void setServerConfiguration (int argc, char *argv[], const std::string &serverConfigurationFile=std::string())
 Configures the HTTP(S) server or FastCGI process. More...
WT_API void addEntryPoint (EntryPointType type, ApplicationCreator callback, const std::string &path=std::string(), const std::string &favicon=std::string())
 Binds an entry-point to a callback function to create a new application. More...
WT_API void addResource (WResource *resource, const std::string &path)
 Binds a resource to a fixed path. More...
WT_API void removeEntryPoint (const std::string &path)
 Removes an entry point. More...
WTCONNECTOR_API bool start ()
 Starts the server in the background. More...
WTCONNECTOR_API void stop ()
 Stops the server. More...
WTCONNECTOR_API bool isRunning () const
 Returns whether the server is running. More...
 Starts the server, waits for shutdown, then stops the server. More...
WTCONNECTOR_API void resume ()
 Resumes the server. More...
WTCONNECTOR_API int httpPort () const
 Returns the server HTTP port number. More...
WT_API std::string appRoot () const
 Returns the approot special property. More...
WT_API void post (const std::string &sessionId, const std::function< void()> &function, const std::function< void()> &fallBackFunction=std::function< void()>())
 Posts a function to a session. More...
WT_API void postAll (const std::function< void()> &function)
 Posts a function to all currently active sessions. More...
WTCONNECTOR_API void setSslPasswordCallback (const SslPasswordCallback &cb)
 Change input method for server certificate passwords (http backend) More...
WT_API bool readConfigurationProperty (const std::string &name, std::string &value) const
 Reads a configuration property. More...
WT_API void setLocalizedStrings (const std::shared_ptr< WLocalizedStrings > &stringResolver)
 Sets the resource object that provides localized strings. More...
WT_API std::shared_ptr< WLocalizedStringslocalizedStrings () const
 Sets the resource object that provides localized strings. More...
WTCONNECTOR_API std::vector< SessionInfosessions () const
 Retrieve information on all sessions. More...
WT_API WLoggerlogger ()
 Returns the logger instance. More...
WT_API WLogEntry log (const std::string &type) const
 Adds an entry to the log. More...
WT_API bool dedicatedSessionProcess () const
 Reflects whether the current process is a dedicated session process.

Static Public Member Functions

static WServerinstance ()
 Returns the server instance. More...
static WT_API int waitForShutdown ()
 Waits for a shutdown signal. More...
static WT_API void restart (int argc, char **argv, char **envp)
 A utility method to restart. More...

Related Functions

(Note that these are not member functions.)

int WRun (int argc, char **argv, ApplicationCreator createApplication=0)
 Runs the Wt application server. More...

Detailed Description

A class encapsulating a web application server.

This server class represents an instance of an application server.

It offers support for multiple application entry points and control over starting and stopping the server. This may be used as an alternative to using WRun() when you wish to support multiple application entry points, or for integrating a Wt (stand-alone httpd) server application into an existing application, with control over starting and stopping the server as appropriate.

As an example usage, consider the implementation of WRun(), which starts the server until a Ctrl-C is pressed or a termination signal has been received, or a restart is indicated using SIGHUP or a changed binary (argv[0]):

int WRun(int argc, char *argv[], ApplicationCreator createApplication)
try {
// use argv[0] as the application name to match a suitable entry
// in the Wt configuration file, and use the default configuration
// file (which defaults to /etc/wt/wt_config.xml unless the environment
// variable WT_CONFIG_XML is set)
WServer server(argv[0]);
// WTHTTP_CONFIGURATION is e.g. "/etc/wt/wthttpd"
server.setServerConfiguration(argc, argv, WTHTTP_CONFIGURATION);
// add a single entry point, at the default location (as determined
// by the server configuration's deploy-path)
server.addEntryPoint(Wt::EntryPointType::Application, createApplication);
if (server.start()) {
int sig = WServer::waitForShutdown(argv[0]);
std::cerr << "Shutdown (signal = " << sig << ")" << std::endl;
if (sig == SIGHUP)
WServer::restart(argc, argv, environ);
} catch (WServer::Exception& e) {
std::cerr << e.what() << "\n";
return 1;
} catch (std::exception& e) {
std::cerr << "exception: " << e.what() << "\n";
return 1;

Constructor & Destructor Documentation

Wt::WServer::WServer ( const std::string &  wtApplicationPath = std::string(),
const std::string &  wtConfigurationFile = std::string() 

Creates a new server instance.

The wtApplicationPath is used to match specific application-settings in the Wt configuration file. If no specific match could be found, the general settings are used (corresponding to the '*' selector).

The Wt application configuration is read from the wtConfigurationFile. If empty, this defaults to the value configured at build time.

For more information on configuring Wt applications, see Configuration.

Exception: indicates a configuration problem.
See also
WTCONNECTOR_API Wt::WServer::WServer ( int  argc,
char *  argv[],
const std::string &  wtConfigurationFile = std::string() 

Creates a new server instance and configures it.

This is equivalent to:

WServer server(argv[0]);
server.setServerConfiguration(argc, argv, wtConfigurationFile);
Exception: indicates a configuration problem.
See also
WServer(const std::string&, const std::string&)
Wt::WServer::~WServer ( )


If the server was still running, it is stopped first by calling stop(). It is probably safer to call stop() first yourself, since this allows exceptions to be caught.

See also
isRunning(), stop()

Member Function Documentation

void Wt::WServer::addEntryPoint ( EntryPointType  type,
ApplicationCreator  callback,
const std::string &  path = std::string(),
const std::string &  favicon = std::string() 

Binds an entry-point to a callback function to create a new application.

The path is the local URL at which the application is deployed: when a user visits this URL, the callback will be called to create a new application. If empty, the URL is inferred from the server configuration's deploy-path (see also Built-in httpd configuration).

The path must start with a '/'.

The optional favicon is a URL path (which should not contain the host part!) to a favicon, which is the icon displayed in the browser for your application. Alternatively, you may specify a favicon using the "favicon" property in the configuration file (see als EntryPointType::Applicationsettings (wt_config.xml)").

See also
void Wt::WServer::addResource ( WResource resource,
const std::string &  path 

Binds a resource to a fixed path.

Resources may either be private to a single session or public. Use this method to add a public resource with a fixed path.

See also
std::string Wt::WServer::appRoot ( ) const

Returns the approot special property.

See also
WTCONNECTOR_API int Wt::WServer::httpPort ( ) const

Returns the server HTTP port number.

Returns -1 if the port is not known (i.e. because the connector is not aware of how the http server is configured).

If the server listens on multiple ports, only the first port is returned.
static WServer* Wt::WServer::instance ( )

Returns the server instance.

Returns the single server instance. This may be useful when using WRun(), which does not provide direct access to the instantiated server, but still you want to use functions like post().

When instantiating multiple servers, this will simply return the last instance. You probably want to avoid this function then.
WIOService & Wt::WServer::ioService ( )

Returns the I/O service.

See also
WTCONNECTOR_API bool Wt::WServer::isRunning ( ) const

Returns whether the server is running.

See also
start(), stop()
std::shared_ptr< WLocalizedStrings > Wt::WServer::localizedStrings ( ) const

Sets the resource object that provides localized strings.

See also
WLogEntry Wt::WServer::log ( const std::string &  type) const

Adds an entry to the log.

See also
Wt::log(), WApplication::log()
WLogger & Wt::WServer::logger ( )

Returns the logger instance.

This is the logger class used in WApplication::log() and Wt::log() functions.

void Wt::WServer::post ( const std::string &  sessionId,
const std::function< void()> &  function,
const std::function< void()> &  fallBackFunction = std::function<void ()>() 

Posts a function to a session.

This is a thread-safe method to post a particular event (implemented as a function object) to be run within the context of a session, identified by its WApplication::sessionId(). The method will safely handle the case where the session is being terminated, and the session lock will be taken to execute the function in the context of the session (with WApplication::instance() pointing to the correct application), just as with a request initiated by the browser. You will typically also want to push the changes to the client using server-initiated updates (WApplication::triggerUpdate()).

The method returns immediately, and the function will be run within the thread-pool that handles incoming web requests. In this way, it avoids dead-lock scenarios.

If a fallbackFunction is specified then in case the session is dead, it is called instead.

This provides a good alternative to grabbing the update lock of an application to directly push changes to a session out of its event loop.

Note that if you post an event to a method of a widget (or other object), it may still be that the targeted object has been deleted, if the life-time of that object is not the same as the life-time of the application. It may be useful to protect yourself from this by using WApplication::bind().

void Wt::WServer::postAll ( const std::function< void()> &  function)

Posts a function to all currently active sessions.

See also
bool Wt::WServer::readConfigurationProperty ( const std::string &  name,
std::string &  value 
) const

Reads a configuration property.

As properties are unique to an executable location, they are defined from the moment that setServerConfiguration() is invoked. Use this method to access configuration properties outside of an active session, e.g. from within the main() function.

See also
void Wt::WServer::removeEntryPoint ( const std::string &  path)

Removes an entry point.

Use this method to remove an entry point or static resource.

In a multi-threaded environment, this may only be done when the server is not running.

When a resource has been bound to the path, the resource will not be deleted.

See also
addEntryPoint(), addResource()
void Wt::WServer::restart ( int  argc,
char **  argv,
char **  envp 

A utility method to restart.

This will result the application with the new image (argv[0]), effectively loading a newly deployed version. (Experimental, UNIX only)

WTCONNECTOR_API void Wt::WServer::resume ( )

Resumes the server.

This closes and reopens the listen socket(s) for accepting new TCP and/or SSL connections. This may be needed when the OS (like IPhoneOS) has closed the sockets while suspending the application.

WTCONNECTOR_API void Wt::WServer::run ( )

Starts the server, waits for shutdown, then stops the server.

This is equivalent to:

See also
WTCONNECTOR_API std::vector<SessionInfo> Wt::WServer::sessions ( ) const

Retrieve information on all sessions.

This is only implemented for the wthttp connector.

If the dedicated process session policy is used, only the original process has access to the full list of sessions. Public resources (those registered with addResource()) run in the original process, so they can access this list.

void Wt::WServer::setIOService ( WIOService ioService)

Sets the I/O service.

The server will use an I/O service for scheduling functions into a thread-pool, and to implement asynchronous networking, whose call-back funtions are scheduled in the same thread pool.

By default, a server will create its own I/O service, but you may configure it to reuse another I/O service.

void Wt::WServer::setLocalizedStrings ( const std::shared_ptr< WLocalizedStrings > &  stringResolver)

Sets the resource object that provides localized strings.

This is used only for WString::tr() used from within static resources.

The default value is 0.

WTCONNECTOR_API void Wt::WServer::setServerConfiguration ( int  argc,
char *  argv[],
const std::string &  serverConfigurationFile = std::string() 

Configures the HTTP(S) server or FastCGI process.

Configures the HTTP(S) server using command-line arguments, a configuration file, or both. The valid options are described in Built-in httpd configuration.

The applications themselves are configured using the configuration file passed to the constructor.

The server configuration must be set before any other functionality can be used.

In case of FastCGI deployment, the serverConfigurationFile argument is ignored, and depending on the command-line arguments, this process may become a FastCGI protocol relay process which never returning from this call but directs the FastCGI stream to the correct session, rather than a Wt application server.

Exception: indicates a configuration problem.
WTCONNECTOR_API void Wt::WServer::setSslPasswordCallback ( const SslPasswordCallback &  cb)

Change input method for server certificate passwords (http backend)

The private server identity key may be protected by a password. If you want to control how the password is retrieved, set a password handler by calling this function. If no password handler is set, the OpenSSL default handler will be used, which asks to enter the password on stdio.

This function must be called before calling start().

The max_length parameter is informational and indicates that the underlying implementation will truncate the password to this length.

WTCONNECTOR_API bool Wt::WServer::start ( )

Starts the server in the background.

Returns whether the server could be successfully started.

Exception: indicates a problem starting the server.
See also
isRunning(), stop()
WTCONNECTOR_API void Wt::WServer::stop ( )

Stops the server.

All active application sessions are terminated cleanly, and the HTTP(S) server is shut down.

This will also stop the underlying ioService(), and will block until all pending tasks have completed.
Exception: indicates a problem while stopping the server.
See also
isRunning(), start()
int Wt::WServer::waitForShutdown ( )

Waits for a shutdown signal.

This static method blocks the current thread, waiting for a shutdown signal. The implementation and details are platform dependent, but this is usually Ctrl-C (SIGINT) or SIGKILL.

This method is convenient if you want to customize how the server is started (by instantiating a WServer object yourself, instead of using Wt::WRun()), but still want to use Wt as a standalone server that cleanly terminates on interruption.

This will also catch SIGHUP, to reread the configuration file.

Friends And Related Function Documentation

int WRun ( int  argc,
char **  argv,
ApplicationCreator  createApplication = 0 

Runs the Wt application server.

This function runs the application server, and should be called only once (e.g. from within your main function).

The createApplication parameter is a std::function object that should create a new application instance for a new user visiting the application. It is of type: std::function<Wt::WApplication* (const Wt::WEnvironment&)>, and thus you can pass to it a function like:

Wt::WApplication *createApplication(const Wt::WEnvironment& env)
  // ...

When using the built-in httpd, the implementation listens for POSIX termination signals (or console CTRL-C) event. You can use the WServer class for more flexible control on starting and stopping the server.

See also

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