HTTP Server API¶

General¶

cpp-netlib includes and implements two distinct HTTP server implementations that you can use and embed in your own applications. Both HTTP Server implementations:

Cannot be copied. This means you may have to store instances of the HTTP Server in dynamic memory if you intend to use them as function parameters or pass them around in smart pointers of by reference.

Assume that requests made are independent of each other. None of the HTTP Server implementations support request pipelining (yet) so a single connection only deals with a single request.

Are header-only and are compiled-into your application. Future releases in case you want to upgrade the implementation you are using in your application will be distributed as header-only implementations, which means you have to re-compile your application to use a newer version of the implementations.

The HTTP Servers have different semantics, and in some cases require different APIs from the supplied template parameters.

Implementations¶

There are two different user-facing template classes that differentiate the Synchronous Servers from the Asynchronous Servers. Both templates take a single template parameter named Handler which describes the type of the Handler function object.

There are two different Handler concepts, one concept for Synchronous Servers and another for Asynchronous Servers.

The SynchronusHandler concept for Synchronous Servers is described by the following table:

Legend:

H: The Handler type.
h: An instance of H.
Req: A type that models the Request Concept.
Res: A type that models the Response Concept.
req: An instance of Req.
res: An instance of Res.

Construct	Return Type	Description
`h(req,res)`	`void`	Handle the request; res is passed in as a non-const lvalue, which represents the response to be returned to the client performing the request.

More information about the internals of the Synchronous Servers can be found in the following section.

The AsynchronousHandler concept for Asynchronous Servers is described by the following table:

Legend:

H: The Handler type.
h: An instance of H.
Req: A type that models the Request Concept.
ConnectionPtr: A type that models the Connection Pointer Concept.
req: An instance of Req.
conn: An instance of ConncetionPtr.

Construct	Return Type	Description
`h(req, conn)`	`void`	Handle the request; conn is a shared pointer which exposes functions for writing to and reading from the connection.

More information about the internals of the Asynchronous Servers can be found in the following section.

Synchronous Servers¶

The synchronous server implementation is represented by the template server in namespace boost::network::http. The server template takes in a single template parameter named Handler which models the SynchronousHandler concept (described above).

An instance of Handler is taken in by reference to the constructor of the HTTP server. This means the Handler is not copied around and only a single instance of the handler is used for all connections and requests performed against the HTTP server.

Warning

It is important to note that the HTTP server does not implement any locking upon invoking the Handler. In case you have any state in the Handler that will be associated with the synchronous server, you would have to implement your own synchronization internal to the Handler implementation. This matters especially if you run the synchronous server in multiple threads.

The general pattern of usage for the HTTP Server template is shown below:

struct handler;
typedef boost::network::http::server<handler> http_server;

struct handler {
    void operator()(
        http_server::request const & req,
        http_server::response & res
    ) {
        // do something, and then edit the res object here.
    }
};

More information about the actual HTTP Server API follows in the next section. It is important to understand that the HTTP Server is actually embedded in your application, which means you can expose almost all your application logic through the Handler type, which you can also initialize appropriately.

API Documentation¶

The following sections assume that the following file has been included:

#include <boost/network/include/http/server.hpp>

And that the following typedef’s have been put in place:

struct handler_type;
typedef boost::network::http::server<handler_type> http_server;

struct handler_type {
    void operator()(
        http_server::request const & request,
        http_server::response & response
    ) {
        // do something here
    }
};

Constructor¶

http_server(address, port, handler): Construct an HTTP Server instance, passing in the address and port as std::string const & and handler being of type handler_type but passed in as an lvalue reference.

Public Members¶

The following definitions assume that a properly constructed http_server instance has been constructed in the following manner:

handler_type handler;
http_server server("127.0.0.1", "8000", handler);

server.run(): Run the HTTP Server event loop. This function can be run on multiple threads following the example:

boost::thread t1(boost::bind(&http_server::run, &server));
boost::thread t2(boost::bind(&http_server::run, &server));
server.run();
t1.join();
t2.join();

server.stop(): Stop the HTTP Server acceptor and wait for all pending requests to finish.

Response Object¶

The response object has its own public member functions which can be very helpful in certain simple situations.

response = http_server::response::stock_reply(status, body): Code like the above should go inside the handler’s operator() overload. The body parameter is an std::string. The status parameter is any of the following values from the http_server::response enum status_type:

enum status_type {
    ok = 200,
    created = 201,
    accepted = 202,
    no_content = 204,
    multiple_choices = 300,
    moved_permanently = 301,
    moved_temporarily = 302,
    not_modified = 304,
    bad_request = 400,
    unauthorized = 401,
    forbidden = 403,
    not_found = 404,
    not_supported = 405,
    not_acceptable = 406,
    internal_server_error = 500,
    not_implemented = 501,
    bad_gateway = 502,
    service_unavailable = 503
};

The response object also has the following publicly accessible member values which can be directly manipulated by the handler.

Member Name	Type	Description
status	`status_type`	The HTTP status of the response.
headers	`vector<header>`	Vector of headers. [1]
content	`string_type` [2]	The contents of the response.

[1]	A header is a struct of type `response_header<http::tags::http_server>`. An instance always has the members `name` and `value` both of which are of type `string_type`.

[2]	`string_type` is `boost::network::string<http::tags::http_server>::type`.

Asynchronous Servers¶

The asynchronous server implementation is significantly different to the synchronous server implementation in three ways:

The Handler instance is invoked asynchronously. This means the I/O thread used to handle network-related events are free to handle only the I/O related events. This enables the server to scale better as to the number of concurrent connections it can handle.

The Handler is able to schedule asynchronous actions on the thread pool associated with the server. This allows handlers to perform multiple asynchronous computations that later on perform writes to the connection.

The Handler is able to control the (asynchronous) writes to and reads from the HTTP connection. Because the connection is available to the Handler, that means it can write out chunks of data at a time or stream data through the connection continuously.

The asynchronous server is meant to allow for better scalability in terms of the number of concurrent connections and for performing asynchronous actions within the handlers. If your applacation does not need to write out information asynchronously or perform potentially long computations, then the synchronous server gives a generally better performance profile than the asynchronous server.

The asynchronous server implementation is available from a single user-facing template named async_server. This template takes in a single template parameter which is the type of the Handler to be called once a request has been parsed from a connection.

An instance of Handler is taken as a reference to the constructor similar to the synchronous server implementation.

Warning

The asynchronous server implementation, like the synchronous server implementation, does not perform any synchronization on the calls to the Handler invocation. This means if your handler contains or maintains internal state, you are responsible for implementing your own synchronization on accesses to the internal state of the Handler.

The general pattern for using the async_server template is shown below:

struct handler;
typedef boost::network::http::async_server<handler> http_server;

struct handler {
    void operator()(
        http_server::request const & req,
        http_server::connection_ptr connection
    ) {
        // handle the request here, and use the connection to
        // either read more data or write data out to the client
    }
};

API Documentation¶

The following sections assume that the following file has been included:

#include <boost/network/include/http/server.hpp>
#include <boost/network/utils/thread_pool.hpp>

And that the following typedef’s have been put in place:

struct handler_type;
typedef boost::network::http::server<handler_type> http_server;

struct handler_type {
    void operator()(
        http_server::request const & request,
        http_server::connection_ptr connection
    ) {
        // do something here
    }
};

Constructor¶

http_server(address, port, handler, thread_pool): Construct an HTTP Server instance, passing in the address and port as std::string const & and handler being of type handler_type but passed in as an lvalue reference. The thread_pool parameter is an instance of boost::network::utils::thread_pool that has been previously instantiated.

Note

The boost::network::utils::thread_pool has a single constructor parameter which is the number of threads to run the thread pool.

Public Members¶

The following definitions assume that a properly constructed http_server instance has been constructed in the following manner:

handler_type handler;
boost::network::utils::thread_pool thread_pool(2);
http_server server("127.0.0.1", "8000", handler, thread_pool);

server.run(): Run the HTTP Server event loop. This function can be run on multiple threads following the example:

boost::thread t1(boost::bind(&http_server::run, &server));
boost::thread t2(boost::bind(&http_server::run, &server));
server.run();
t1.join();
t2.join();

server.stop(): Stop the HTTP Server acceptor and wait for all pending requests to finish.

Connection Object¶

The connection object has its own public member functions which will be the primary means for reading from and writing to the connection.

template <class Range> write(Range range)

The connection object exposes a function write that can be given a parameter that adheres to the Boost.Range Single Pass Range Concept. The write function, although it looks synchronous, starts of a series of asynchronous writes to the connection as soon as the range is serialized to appropriately sized buffers.

To use this in your handler, it would look something like this:

connection->write("Hello, world!");
std::string sample = "I have a string!";
connection->write(sample);

template <class Range, class Callback> void write(Range range, Callback callback)

The connection object also exposes a function write that can be given a parameter that adheres to the Boost.Range Single Pass Range Concept, as well as a Callback function that returns void and takes a boost::system::error_code as a parameter. This overload of write is useful for writing streaming applications that send out chunks of data at a time, or for writing data that may not all fit in memory right away.

template <class ReadCallback> void read(ReadCallback callback)

The connection object has a function read which can be used to read more information from the connection. This read function takes in a callback that can be assigned to a Boost.Function with the signature void(input_range,error_code,size_t,connection_ptr). The following list shows what the types actually mean:

input_range – boost::iterator_range<char const *> : The range that denotes the data read from the connection.

error_code – boost::system::error_code : The error code if there were any errors encountered from the read.

size_t – std::size_t : The number of bytes transferred.

connection_ptr – http_server::connection_ptr : A handle to the current connection, so that it is kept alive at the time of the read callback invocation.

This interface is useful when doing reads of uploaded data that can be potentially large and may not fit in memory. The read handler is then responsible for dealing with the chunks of data available from the connection.

void set_status(status_t new_status)

The set_status function takes a parameter of type status_t which is an enum type nested in http_status::connection which is given in the following code listing.

enum status_t {
    ok = 200
    , created = 201
    , accepted = 202
    , no_content = 204
    , multiple_choices = 300
    , moved_permanently = 301
    , moved_temporarily = 302
    , not_modified = 304
    , bad_request = 400
    , unauthorized = 401
    , forbidden = 403
    , not_found = 404
    , not_supported = 405
    , not_acceptable = 406
    , internal_server_error = 500
    , not_implemented = 501
    , bad_gateway = 502
    , service_unavailable = 503
};

Note

You may set and re-set the status several times as long as you have not set the headers or sent data through the connection. If you do this after data has already been set, the function will throw an instance of std::logic_error.

template <class Range> void set_headers(Range range)

The set_headers function takes a Single Pass Range of boost::network::http::response_header<http::tags::http_async_server> instances and linearizes them to a buffer with at most BOOST_NETWORK_HTTP_SERVER_CONNECTION_HEADER_BUFFER_MAX_SIZE and immediately schedules an asynchronous write once that is done.

The function throws an instance of std::logic_error if you try to set the headers for a connection more than once.

cpp-netlib v0.8 documentation

HTTP Server API¶

General¶

Implementations¶

Synchronous Servers¶

API Documentation¶

Constructor¶

Public Members¶

Response Object¶

Asynchronous Servers¶

API Documentation¶

Constructor¶

Public Members¶

Connection Object¶

Table Of Contents

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cpp-netlib v0.8 documentation

HTTP Server API¶

General¶

Implementations¶

Synchronous Servers¶

API Documentation¶

Constructor¶

Public Members¶

Response Object¶

Asynchronous Servers¶

API Documentation¶

Constructor¶

Public Members¶

Connection Object¶

Table Of Contents

Browse

You are here:

This Page

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