cpp-httplib

A C++11 single-file header-only cross platform HTTP/HTTPS library.

It's extremely easy to setup. Just include the httplib.h file in your code!

[!IMPORTANT] This library uses 'blocking' socket I/O. If you are looking for a library with 'non-blocking' socket I/O, this is not the one that you want.

Simple examples

Server (Multi-threaded)

#define CPPHTTPLIB_OPENSSL_SUPPORT
#include "path/to/httplib.h"

// HTTP
httplib::Server svr;

// HTTPS
httplib::SSLServer svr;

svr.Get("/hi", [](const httplib::Request &, httplib::Response &res) {
  res.set_content("Hello World!", "text/plain");
});

svr.listen("0.0.0.0", 8080);

Client

#define CPPHTTPLIB_OPENSSL_SUPPORT
#include "path/to/httplib.h"

// HTTP
httplib::Client cli("http://cpp-httplib-server.yhirose.repl.co");

// HTTPS
httplib::Client cli("https://cpp-httplib-server.yhirose.repl.co");

auto res = cli.Get("/hi");
res->status;
res->body;

SSL Support

SSL support is available with CPPHTTPLIB_OPENSSL_SUPPORT. libssl and libcrypto should be linked.

[!NOTE] cpp-httplib currently supports only version 3.0 or later. Please see this page to get more information.

[!TIP] For macOS: cpp-httplib now can use system certs with CPPHTTPLIB_USE_CERTS_FROM_MACOSX_KEYCHAIN. CoreFoundation and Security should be linked with -framework.

#define CPPHTTPLIB_OPENSSL_SUPPORT
#include "path/to/httplib.h"

// Server
httplib::SSLServer svr("./cert.pem", "./key.pem");

// Client
httplib::Client cli("https://localhost:1234"); // scheme + host
httplib::SSLClient cli("localhost:1234"); // host
httplib::SSLClient cli("localhost", 1234); // host, port

// Use your CA bundle
cli.set_ca_cert_path("./ca-bundle.crt");

// Disable cert verification
cli.enable_server_certificate_verification(false);

// Disable host verification
cli.enable_server_hostname_verification(false);

[!NOTE] When using SSL, it seems impossible to avoid SIGPIPE in all cases, since on some operating systems, SIGPIPE can only be suppressed on a per-message basis, but there is no way to make the OpenSSL library do so for its internal communications. If your program needs to avoid being terminated on SIGPIPE, the only fully general way might be to set up a signal handler for SIGPIPE to handle or ignore it yourself.

Server

#include <httplib.h>

int main(void)
{
  using namespace httplib;

  Server svr;

  svr.Get("/hi", [](const Request& req, Response& res) {
    res.set_content("Hello World!", "text/plain");
  });

  // Match the request path against a regular expression
  // and extract its captures
  svr.Get(R"(/numbers/(\d+))", [&](const Request& req, Response& res) {
    auto numbers = req.matches[1];
    res.set_content(numbers, "text/plain");
  });

  // Capture the second segment of the request path as "id" path param
  svr.Get("/users/:id", [&](const Request& req, Response& res) {
    auto user_id = req.path_params.at("id");
    res.set_content(user_id, "text/plain");
  });

  // Extract values from HTTP headers and URL query params
  svr.Get("/body-header-param", [](const Request& req, Response& res) {
    if (req.has_header("Content-Length")) {
      auto val = req.get_header_value("Content-Length");
    }
    if (req.has_param("key")) {
      auto val = req.get_param_value("key");
    }
    res.set_content(req.body, "text/plain");
  });

  svr.Get("/stop", [&](const Request& req, Response& res) {
    svr.stop();
  });

  svr.listen("localhost", 1234);
}

Post, Put, Delete and Options methods are also supported.

Bind a socket to multiple interfaces and any available port

int port = svr.bind_to_any_port("0.0.0.0");
svr.listen_after_bind();

Static File Server

// Mount / to ./www directory
auto ret = svr.set_mount_point("/", "./www");
if (!ret) {
  // The specified base directory doesn't exist...
}

// Mount /public to ./www directory
ret = svr.set_mount_point("/public", "./www");

// Mount /public to ./www1 and ./www2 directories
ret = svr.set_mount_point("/public", "./www1"); // 1st order to search
ret = svr.set_mount_point("/public", "./www2"); // 2nd order to search

// Remove mount /
ret = svr.remove_mount_point("/");

// Remove mount /public
ret = svr.remove_mount_point("/public");

// User defined file extension and MIME type mappings
svr.set_file_extension_and_mimetype_mapping("cc", "text/x-c");
svr.set_file_extension_and_mimetype_mapping("cpp", "text/x-c");
svr.set_file_extension_and_mimetype_mapping("hh", "text/x-h");

The followings are built-in mappings:

[!WARNING] These static file server methods are not thread-safe.

File request handler

// The handler is called right before the response is sent to a client
svr.set_file_request_handler([](const Request &req, Response &res) {
  ...
});

Logging

svr.set_logger([](const auto& req, const auto& res) {
  your_logger(req, res);
});

Error handler

svr.set_error_handler([](const auto& req, auto& res) {
  auto fmt = "<p>Error Status: <span style='color:red;'>%d</span></p>";
  char buf[BUFSIZ];
  snprintf(buf, sizeof(buf), fmt, res.status);
  res.set_content(buf, "text/html");
});

Exception handler

The exception handler gets called if a user routing handler throws an error.

svr.set_exception_handler([](const auto& req, auto& res, std::exception_ptr ep) {
  auto fmt = "<h1>Error 500</h1><p>%s</p>";
  char buf[BUFSIZ];
  try {
    std::rethrow_exception(ep);
  } catch (std::exception &e) {
    snprintf(buf, sizeof(buf), fmt, e.what());
  } catch (...) { // See the following NOTE
    snprintf(buf, sizeof(buf), fmt, "Unknown Exception");
  }
  res.set_content(buf, "text/html");
  res.status = StatusCode::InternalServerError_500;
});

[!CAUTION] if you don't provide the catch (...) block for a rethrown exception pointer, an uncaught exception will end up causing the server crash. Be careful!

Pre routing handler

svr.set_pre_routing_handler([](const auto& req, auto& res) {
  if (req.path == "/hello") {
    res.set_content("world", "text/html");
    return Server::HandlerResponse::Handled;
  }
  return Server::HandlerResponse::Unhandled;
});

Post routing handler

svr.set_post_routing_handler([](const auto& req, auto& res) {
  res.set_header("ADDITIONAL_HEADER", "value");
});

'multipart/form-data' POST data

svr.Post("/multipart", [&](const auto& req, auto& res) {
  auto size = req.files.size();
  auto ret = req.has_file("name1");
  const auto& file = req.get_file_value("name1");
  // file.filename;
  // file.content_type;
  // file.content;
});

Receive content with a content receiver

svr.Post("/content_receiver",
  [&](const Request &req, Response &res, const ContentReader &content_reader) {
    if (req.is_multipart_form_data()) {
      // NOTE: `content_reader` is blocking until every form data field is read
      MultipartFormDataItems files;
      content_reader(
        [&](const MultipartFormData &file) {
          files.push_back(file);
          return true;
        },
        [&](const char *data, size_t data_length) {
          files.back().content.append(data, data_length);
          return true;
        });
    } else {
      std::string body;
      content_reader([&](const char *data, size_t data_length) {
        body.append(data, data_length);
        return true;
      });
    }
  });

Send content with the content provider

const size_t DATA_CHUNK_SIZE = 4;

svr.Get("/stream", [&](const Request &req, Response &res) {
  auto data = new std::string("abcdefg");

  res.set_content_provider(
    data->size(), // Content length
    "text/plain", // Content type
    [&, data](size_t offset, size_t length, DataSink &sink) {
      const auto &d = *data;
      sink.write(&d[offset], std::min(length, DATA_CHUNK_SIZE));
      return true; // return 'false' if you want to cancel the process.
    },
    [data](bool success) { delete data; });
});

Without content length:

svr.Get("/stream", [&](const Request &req, Response &res) {
  res.set_content_provider(
    "text/plain", // Content type
    [&](size_t offset, DataSink &sink) {
      if (/* there is still data */) {
        std::vector<char> data;
        // prepare data...
        sink.write(data.data(), data.size());
      } else {
        sink.done(); // No more data
      }
      return true; // return 'false' if you want to cancel the process.
    });
});

Chunked transfer encoding

svr.Get("/chunked", [&](const Request& req, Response& res) {
  res.set_chunked_content_provider(
    "text/plain",
    [](size_t offset, DataSink &sink) {
      sink.write("123", 3);
      sink.write("345", 3);
      sink.write("789", 3);
      sink.done(); // No more data
      return true; // return 'false' if you want to cancel the process.
    }
  );
});

With trailer:

svr.Get("/chunked", [&](const Request& req, Response& res) {
  res.set_header("Trailer", "Dummy1, Dummy2");
  res.set_chunked_content_provider(
    "text/plain",
    [](size_t offset, DataSink &sink) {
      sink.write("123", 3);
      sink.write("345", 3);
      sink.write("789", 3);
      sink.done_with_trailer({
        {"Dummy1", "DummyVal1"},
        {"Dummy2", "DummyVal2"}
      });
      return true;
    }
  );
});

Send file content

svr.Get("/content", [&](const Request &req, Response &res) {
  res.set_file_content("./path/to/conent.html");
});

svr.Get("/content", [&](const Request &req, Response &res) {
  res.set_file_content("./path/to/conent", "text/html");
});

'Expect: 100-continue' handler

By default, the server sends a 100 Continue response for an Expect: 100-continue header.

// Send a '417 Expectation Failed' response.
svr.set_expect_100_continue_handler([](const Request &req, Response &res) {
  return StatusCode::ExpectationFailed_417;
});

// Send a final status without reading the message body.
svr.set_expect_100_continue_handler([](const Request &req, Response &res) {
  return res.status = StatusCode::Unauthorized_401;
});

Keep-Alive connection

svr.set_keep_alive_max_count(2); // Default is 5
svr.set_keep_alive_timeout(10);  // Default is 5

Timeout

svr.set_read_timeout(5, 0); // 5 seconds
svr.set_write_timeout(5, 0); // 5 seconds
svr.set_idle_interval(0, 100000); // 100 milliseconds

Set maximum payload length for reading a request body

svr.set_payload_max_length(1024 * 1024 * 512); // 512MB

[!NOTE] When the request body content type is 'www-form-urlencoded', the actual payload length shouldn't exceed CPPHTTPLIB_FORM_URL_ENCODED_PAYLOAD_MAX_LENGTH.

Server-Sent Events

Please see Server example and Client example.

Default thread pool support

ThreadPool is used as a default task queue, and the default thread count is 8, or std::thread::hardware_concurrency(). You can change it with CPPHTTPLIB_THREAD_POOL_COUNT.

If you want to set the thread count at runtime, there is no convenient way... But here is how.

svr.new_task_queue = [] { return new ThreadPool(12); };

You can also provide an optional parameter to limit the maximum number of pending requests, i.e. requests accept()ed by the listener but still waiting to be serviced by worker threads.

svr.new_task_queue = [] { return new ThreadPool(/*num_threads=*/12, /*max_queued_requests=*/18); };

Default limit is 0 (unlimited). Once the limit is reached, the listener will shutdown the client connection.

Override the default thread pool with yours

You can supply your own thread pool implementation according to your need.

class YourThreadPoolTaskQueue : public TaskQueue {
public:
  YourThreadPoolTaskQueue(size_t n) {
    pool_.start_with_thread_count(n);
  }

  virtual bool enqueue(std::function<void()> fn) override {
    /* Return true if the task was actually enqueued, or false
     * if the caller must drop the corresponding connection. */
    return pool_.enqueue(fn);
  }

  virtual void shutdown() override {
    pool_.shutdown_gracefully();
  }

private:
  YourThreadPool pool_;
};

svr.new_task_queue = [] {
  return new YourThreadPoolTaskQueue(12);
};

Client

#include <httplib.h>
#include <iostream>

int main(void)
{
  httplib::Client cli("localhost", 1234);

  if (auto res = cli.Get("/hi")) {
    if (res->status == StatusCode::OK_200) {
      std::cout << res->body << std::endl;
    }
  } else {
    auto err = res.error();
    std::cout << "HTTP error: " << httplib::to_string(err) << std::endl;
  }
}

[!TIP] Constructor with scheme-host-port string is now supported!

httplib::Client cli("localhost");
httplib::Client cli("localhost:8080");
httplib::Client cli("http://localhost");
httplib::Client cli("http://localhost:8080");
httplib::Client cli("https://localhost");
httplib::SSLClient cli("localhost");

Error code

Here is the list of errors from Result::error().

enum Error {
  Success = 0,
  Unknown,
  Connection,
  BindIPAddress,
  Read,
  Write,
  ExceedRedirectCount,
  Canceled,
  SSLConnection,
  SSLLoadingCerts,
  SSLServerVerification,
  UnsupportedMultipartBoundaryChars,
  Compression,
  ConnectionTimeout,
};

GET with HTTP headers

httplib::Headers headers = {
  { "Hello", "World!" }
};
auto res = cli.Get("/hi", headers);

or

auto res = cli.Get("/hi", {{"Hello", "World!"}});

or

cli.set_default_headers({
  { "Hello", "World!" }
});
auto res = cli.Get("/hi");

POST

res = cli.Post("/post", "text", "text/plain");
res = cli.Post("/person", "name=john1&note=coder", "application/x-www-form-urlencoded");

POST with parameters

httplib::Params params;
params.emplace("name", "john");
params.emplace("note", "coder");

auto res = cli.Post("/post", params);

or

httplib::Params params{
  { "name", "john" },
  { "note", "coder" }
};

auto res = cli.Post("/post", params);

POST with Multipart Form Data

httplib::MultipartFormDataItems items = {
  { "text1", "text default", "", "" },
  { "text2", "aωb", "", "" },
  { "file1", "h\ne\n\nl\nl\no\n", "hello.txt", "text/plain" },
  { "file2", "{\n  \"world\", true\n}\n", "world.json", "application/json" },
  { "file3", "", "", "application/octet-stream" },
};

auto res = cli.Post("/multipart", items);

PUT

res = cli.Put("/resource/foo", "text", "text/plain");

DELETE

res = cli.Delete("/resource/foo");

OPTIONS

res = cli.Options("*");
res = cli.Options("/resource/foo");

Timeout

cli.set_connection_timeout(0, 300000); // 300 milliseconds
cli.set_read_timeout(5, 0); // 5 seconds
cli.set_write_timeout(5, 0); // 5 seconds

Receive content with a content receiver

std::string body;

auto res = cli.Get("/large-data",
  [&](const char *data, size_t data_length) {
    body.append(data, data_length);
    return true;
  });

std::string body;

auto res = cli.Get(
  "/stream", Headers(),
  [&](const Response &response) {
    EXPECT_EQ(StatusCode::OK_200, response.status);
    return true; // return 'false' if you want to cancel the request.
  },
  [&](const char *data, size_t data_length) {
    body.append(data, data_length);
    return true; // return 'false' if you want to cancel the request.
  });

Send content with a content provider

std::string body = ...;

auto res = cli.Post(
  "/stream", body.size(),
  [](size_t offset, size_t length, DataSink &sink) {
    sink.write(body.data() + offset, length);
    return true; // return 'false' if you want to cancel the request.
  },
  "text/plain");

Chunked transfer encoding

auto res = cli.Post(
  "/stream",
  [](size_t offset, DataSink &sink) {
    sink.os << "chunked data 1";
    sink.os << "chunked data 2";
    sink.os << "chunked data 3";
    sink.done();
    return true; // return 'false' if you want to cancel the request.
  },
  "text/plain");

With Progress Callback

httplib::Client cli(url, port);

// prints: 0 / 000 bytes => 50% complete
auto res = cli.Get("/", [](uint64_t len, uint64_t total) {
  printf("%lld / %lld bytes => %d%% complete\n",
    len, total,
    (int)(len*100/total));
  return true; // return 'false' if you want to cancel the request.
}
);

Authentication

// Basic Authentication
cli.set_basic_auth("user", "pass");

// Digest Authentication
cli.set_digest_auth("user", "pass");

// Bearer Token Authentication
cli.set_bearer_token_auth("token");

[!NOTE] OpenSSL is required for Digest Authentication.

Proxy server support

cli.set_proxy("host", port);

// Basic Authentication
cli.set_proxy_basic_auth("user", "pass");

// Digest Authentication
cli.set_proxy_digest_auth("user", "pass");

// Bearer Token Authentication
cli.set_proxy_bearer_token_auth("pass");

[!NOTE] OpenSSL is required for Digest Authentication.

Range

httplib::Client cli("httpbin.org");

auto res = cli.Get("/range/32", {
  httplib::make_range_header({{1, 10}}) // 'Range: bytes=1-10'
});
// res->status should be 206.
// res->body should be "bcdefghijk".

httplib::make_range_header({{1, 10}, {20, -1}})      // 'Range: bytes=1-10, 20-'
httplib::make_range_header({{100, 199}, {500, 599}}) // 'Range: bytes=100-199, 500-599'
httplib::make_range_header({{0, 0}, {-1, 1}})        // 'Range: bytes=0-0, -1'

Keep-Alive connection

httplib::Client cli("localhost", 1234);

cli.Get("/hello");         // with "Connection: close"

cli.set_keep_alive(true);
cli.Get("/world");

cli.set_keep_alive(false);
cli.Get("/last-request");  // with "Connection: close"

Redirect

httplib::Client cli("yahoo.com");

auto res = cli.Get("/");
res->status; // 301

cli.set_follow_location(true);
res = cli.Get("/");
res->status; // 200

Use a specific network interface

[!NOTE] This feature is not available on Windows, yet.

cli.set_interface("eth0"); // Interface name, IP address or host name

Compression

The server can apply compression to the following MIME type contents:

• all text types except text/event-stream
• image/svg+xml
• application/javascript
• application/json
• application/xml
• application/xhtml+xml

Zlib Support

'gzip' compression is available with CPPHTTPLIB_ZLIB_SUPPORT. libz should be linked.

Brotli Support

Brotli compression is available with CPPHTTPLIB_BROTLI_SUPPORT. Necessary libraries should be linked. Please see https://github.com/google/brotli for more detail.

Default Accept-Encoding value

The default Acdcept-Encoding value contains all possible compression types. So, the following two examples are same.

res = cli.Get("/resource/foo");
res = cli.Get("/resource/foo", {{"Accept-Encoding", "gzip, deflate, br"}});

If we don't want a response without compression, we have to set Accept-Encoding to an empty string. This behavior is similar to curl.

res = cli.Get("/resource/foo", {{"Accept-Encoding", ""}});

Compress request body on client

cli.set_compress(true);
res = cli.Post("/resource/foo", "...", "text/plain");

Compress response body on client

cli.set_decompress(false);
res = cli.Get("/resource/foo");
res->body; // Compressed data

Use poll instead of select

select system call is used as default since it's more widely supported. If you want to let cpp-httplib use poll instead, you can do so with CPPHTTPLIB_USE_POLL.

Unix Domain Socket Support

Unix Domain Socket support is available on Linux and macOS.

// Server
httplib::Server svr("./my-socket.sock");
svr.set_address_family(AF_UNIX).listen("./my-socket.sock", 80);

// Client
httplib::Client cli("./my-socket.sock");
cli.set_address_family(AF_UNIX);

"my-socket.sock" can be a relative path or an absolute path. You application must have the appropriate permissions for the path. You can also use an abstract socket address on Linux. To use an abstract socket address, prepend a null byte ('\x00') to the path.

Split httplib.h into .h and .cc

$ ./split.py -h
usage: split.py [-h] [-e EXTENSION] [-o OUT]

This script splits httplib.h into .h and .cc parts.

optional arguments:
  -h, --help            show this help message and exit
  -e EXTENSION, --extension EXTENSION
                        extension of the implementation file (default: cc)
  -o OUT, --out OUT     where to write the files (default: out)

$ ./split.py
Wrote out/httplib.h and out/httplib.cc

Dockerfile for Static HTTP Server

Dockerfile for static HTTP server is available. Port number of this HTTP server is 80, and it serves static files from /html directory in the container.

> docker build -t cpp-httplib-server .
...

> docker run --rm -it -p 8080:80 -v ./docker/html:/html cpp-httplib-server
Serving HTTP on 0.0.0.0 port 80 ...
192.168.65.1 - - [31/Aug/2024:21:33:56 +0000] "GET / HTTP/1.1" 200 599 "-" "curl/8.7.1"
192.168.65.1 - - [31/Aug/2024:21:34:26 +0000] "GET / HTTP/1.1" 200 599 "-" "Mozilla/5.0 ..."
192.168.65.1 - - [31/Aug/2024:21:34:26 +0000] "GET /favicon.ico HTTP/1.1" 404 152 "-" "Mozilla/5.0 ..."

From Docker Hub

> docker run --rm -it -p 8080:80 -v ./docker/html:/html yhirose4dockerhub/cpp-httplib-server
...

> docker run --init --rm -it -p 8080:80 -v ./docker/html:/html cpp-httplib-server
Serving HTTP on 0.0.0.0 port 80 ...
192.168.65.1 - - [31/Aug/2024:21:33:56 +0000] "GET / HTTP/1.1" 200 599 "-" "curl/8.7.1"
192.168.65.1 - - [31/Aug/2024:21:34:26 +0000] "GET / HTTP/1.1" 200 599 "-" "Mozilla/5.0 ..."
192.168.65.1 - - [31/Aug/2024:21:34:26 +0000] "GET /favicon.ico HTTP/1.1" 404 152 "-" "Mozilla/5.0 ..."

NOTE

g++

g++ 4.8 and below cannot build this library since <regex> in the versions are broken.

Windows

Include httplib.h before Windows.h or include Windows.h by defining WIN32_LEAN_AND_MEAN beforehand.

#include <httplib.h>
#include <Windows.h>

#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include <httplib.h>

[!NOTE] cpp-httplib officially supports only the latest Visual Studio. It might work with former versions of Visual Studio, but I can no longer verify it. Pull requests are always welcome for the older versions of Visual Studio unless they break the C++11 conformance.

[!NOTE] Windows 8 or lower, Visual Studio 2013 or lower, and Cygwin and MSYS2 including MinGW are neither supported nor tested.

License

MIT license (© 2024 Yuji Hirose)

Special Thanks To

These folks made great contributions to polish this library to totally another level from a simple toy!