TLS Setup

So far we've been using plain HTTP, but in the real world, HTTPS is the norm. To use HTTPS with cpp-httplib, you need a TLS library.

In this tour, we'll use OpenSSL. It's the most widely used option, and you'll find plenty of resources online.

Installing OpenSSL

Install it for your OS.

Compile Options

To enable TLS, define the CPPHTTPLIB_OPENSSL_SUPPORT macro when compiling. You'll need a few extra options compared to the previous chapters.

# macOS (Homebrew)
clang++ -std=c++17 -DCPPHTTPLIB_OPENSSL_SUPPORT \
    -I$(brew --prefix openssl)/include \
    -L$(brew --prefix openssl)/lib \
    -lssl -lcrypto \
    -framework CoreFoundation -framework Security \
    -o server server.cpp

# Linux
clang++ -std=c++17 -pthread -DCPPHTTPLIB_OPENSSL_SUPPORT \
    -lssl -lcrypto \
    -o server server.cpp

# Windows (Developer Command Prompt)
cl /EHsc /std:c++17 /DCPPHTTPLIB_OPENSSL_SUPPORT server.cpp libssl.lib libcrypto.lib

# macOS (Homebrew)
clang++ -std=c++17 -DCPPHTTPLIB_OPENSSL_SUPPORT \
    -I$(brew --prefix openssl)/include \
    -L$(brew --prefix openssl)/lib \
    -lssl -lcrypto \
    -framework CoreFoundation -framework Security \
    -o server server.cpp

# Linux
clang++ -std=c++17 -pthread -DCPPHTTPLIB_OPENSSL_SUPPORT \
    -lssl -lcrypto \
    -o server server.cpp

# Windows (Developer Command Prompt)
cl /EHsc /std:c++17 /DCPPHTTPLIB_OPENSSL_SUPPORT server.cpp libssl.lib libcrypto.lib

Let's look at what each option does.

• -DCPPHTTPLIB_OPENSSL_SUPPORT — Defines the macro that enables TLS support
• -lssl -lcrypto — Links the OpenSSL libraries
• -I / -L (macOS only) — Points to the Homebrew OpenSSL paths
• -framework CoreFoundation -framework Security (macOS only) — Needed to automatically load system certificates from the Keychain

Verifying the Setup

Let's make sure everything works. Here's a simple program that passes an HTTPS URL to httplib::Client.

#define CPPHTTPLIB_OPENSSL_SUPPORT
#include "httplib.h"
#include <iostream>

int main() {
    httplib::Client cli("https://www.google.com");

    auto res = cli.Get("/");
    if (res) {
        std::cout << "Status: " << res->status << std::endl;
    } else {
        std::cout << "Error: " << httplib::to_string(res.error()) << std::endl;
    }
}

#define CPPHTTPLIB_OPENSSL_SUPPORT
#include "httplib.h"
#include <iostream>

int main() {
    httplib::Client cli("https://www.google.com");

    auto res = cli.Get("/");
    if (res) {
        std::cout << "Status: " << res->status << std::endl;
    } else {
        std::cout << "Error: " << httplib::to_string(res.error()) << std::endl;
    }
}

Compile and run it. If you see Status: 200, your setup is complete.

Other TLS Backends

cpp-httplib also supports Mbed TLS and wolfSSL in addition to OpenSSL. You can switch between them just by changing the macro definition and linked libraries.

This tour assumes OpenSSL, but the API is the same regardless of which backend you choose.

Next Step

You're all set with TLS. Next, let's send a request to an HTTPS site.

Next: HTTPS Client