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This article mainly introduces "the principle of HTTP client in C++". In daily operation, I believe many people have doubts about the principle of HTTP client in C++. Xiaobian consulted all kinds of information and sorted out simple and easy to use operation methods. I hope to help you answer the doubts of "the principle of HTTP client in C++"! Next, please follow the small series to learn together!

Workflow is an asynchronous scheduling framework, so after this task is issued, it will not block the current thread, plus the internal connection multiplexing, which fundamentally ensures the high performance of our Http Client.

1. Create Http Task

As you can see from the above demo, the request is implemented by initiating a Workflow Http asynchronous task. The interface for creating the task is as follows:

WFHttpTask *create_http_task(const std::string& url,

int redirect_max, int retry_max,

http_callback_t callback);

The first parameter is the URL we want to request. Correspondingly, in the first example, our redirect_max is 2 and retry_max is 3. The fourth parameter is a callback function, in the example we use a lambda, because Workflow tasks are asynchronous, so we process the result of this thing is passively notified to us, the result will call this callback function, the format is as follows:

using http_callback_t = std::function;

2. Fill in the header and send it

Our network interaction is nothing more than request-reply, corresponding to Http Client, after we create a good task, we have some time to process the request, in the Http protocol, that is, fill in the protocol-related things in the header, for example, we can specify a long connection to establish Http through Connection to save time for establishing a connection next time, then we can set Connection to Keep-Alive. Examples are as follows:

protocol::HttpRequest *req = task->get_req();req->add_header_pair("Connection", "Keep-Alive");task->start();

Finally, we will set up the requested task, through task->start(); issued. In the initial http_client.cc example, there is a getchar(); statement because our asynchronous task is non-blocking, the current thread will exit without temporarily stopping, and we want to wait for the callback function to return, so we can pause in a variety of ways.

3. Processing returns results

A return result, according to Http protocol, will contain three parts: message line, message header, message body. If we want to get the body, we can do this:

const void *body;size_t body_len;task->get_resp()->get_parsed_body(&body, &body_len);

Basic guarantee of high performance

We use C++ to write Http Client, the most fragrant is to take advantage of its high performance. How does Workflow guarantee high concurrency? Actually, there are only two points:

Pure asynchronous;

Connection multiplexing;

The former is the reuse of thread resources, the latter is the reuse of connection resources, these framework levels are well managed for users, fully reducing the mental burden of developers.

At this point, the study of "the principle of HTTP client in C++" is over, hoping to solve everyone's doubts. Theory and practice can better match to help you learn, go and try it! If you want to continue learning more relevant knowledge, please continue to pay attention to the website, Xiaobian will continue to strive to bring more practical articles for everyone!

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