Hey there, let's tackle this HTTP 101 error you're hitting with cpprestsdk. That "Failed to connect to any resolved endpoint" message usually points to issues with how your client is reaching the target server, so let's break down the most likely fixes:

1. Double-check your target URL and protocol #

First off, make sure you're using the correct protocol (http:// vs https://) for your endpoint. cpprestsdk's http_client doesn't auto-switch between them—if your server uses HTTPS but you're using an HTTP URL (or vice versa), you'll get this error immediately. Also verify the domain/IP and port are correct—typos here are super common culprits.

Here's a corrected example of setting up a client for an HTTPS endpoint (a frequent pitfall):

#include <cpprest/http_client.h>
#include <cpprest/filestream.h>
#include <cpprest/uri.h>

using namespace utility;
using namespace web;
using namespace web::http;
using namespace web::http::client;

int main() {
    // Use https:// for HTTPS endpoints, http:// for HTTP
    uri_builder uri(L"https://example.com/api");
    http_client client(uri.to_uri());

    // Example GET request
    client.request(methods::GET)
        .then([](http_response response) {
            if (response.status_code() == status_codes::OK) {
                return response.extract_string();
            }
            return pplx::task_from_result(std::wstring(L"Request failed"));
        })
        .wait();

    return 0;
}

2. Fix HTTPS/SSL configuration #

If you're connecting to an HTTPS endpoint, you might need to adjust SSL validation settings—especially if you're testing against a server with a self-signed certificate. By default, cpprestsdk rejects untrusted certificates, which can block the connection.

For development only (never do this in production), you can disable certificate validation:

http_client_config config;
config.set_validate_certificates(false); // Skip cert check for dev environments
http_client client(L"https://your-dev-server.com", config);

For production, load trusted CA certificates properly using config.set_ssl_context_callback() to customize the SSL context with your organization's CA bundle.

3. Rule out network/firewall issues #

• Test if your machine can reach the target server using command-line tools like ping or curl. If those fail, the problem is with your network, not your code.
• Ensure your local firewall or network firewall isn't blocking outgoing connections on the port you're using (80 for HTTP, 443 for HTTPS).
• If you're behind a proxy, configure the client to use it:

http_client_config config;
config.set_proxy(web::web_proxy(L"http://your-proxy-address:port"));
http_client client(L"https://example.com", config);

4. Debug endpoint resolution #

Add some error handling to get more details about which endpoints are failing to connect. This can help you confirm if DNS is resolving the domain correctly, or if the resolved IPs are unreachable:

try {
    auto response = client.request(methods::GET).get();
} catch (const http_exception& e) {
    std::wcout << L"Full error details: " << e.what() << std::endl;
    // This will often list the specific endpoints the client tried and failed to reach
}

内容的提问来源于stack exchange，提问作者Nikhil Wagh