C++ Web Crawling: libcurl in Action

Teach you how to use C++ to play with web crawling

Crawlers know that without a proxy IP, it's like running naked on the Internet, and you'll be hacked by the target website in minutes. Today, let's take the libcurl library in C++ to teach you how to use proxy IP to do data collection safely and efficiently, and focus on our family!ipipgoof agency services.

Why do I have to use a proxy IP?

For example, you continuously use the same IP crazy request website, the server immediately give you a seal. At this time, the proxy IP is like a new vest, each request for a new identity, the site simply can not figure out your routine. Use ouripipgoThe IP pool, each request automatically switch to a different export IP, guaranteed collection is as stable as an old dog.

Libcurl Basic Configuration

First the entire base framework that can run, note these key configurations:

CURL curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_URL, "https://目标网站.com");
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_callback); curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_callback);
curl_easy_setopt(curl, CURLOPT_TIMEOUT, 30L); //30 seconds timeout

Here's a pitfall to watch out for:Remember to enable SSL authentication, otherwise the https request will punt. Add this line of code to keep it safe:

curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 1L);

Proxy IP real-world configuration

Here comes the point! Accessipipgoof agency services in three steps:

// Format: username:password@proxy:port
string proxy = "vip用户:123456@gateway.ipipgo.net:9021";
curl_easy_setopt(curl, CURLOPT_PROXY, proxy.c_str());
curl_easy_setopt(curl, CURLOPT_PROXYTYPE, CURLPROXY_HTTP);

Here's the kicker: if you get a connection timeout, there's an automatic retry mechanism. Let'sipipgoThe IP pool response speed of the IP pool is 200ms on average, and it is recommended to set 3 retries:

curl_easy_setopt(curl, CURLOPT_TIMEOUT, 10L); curl_easy_setopt(curl, CURLOPT_TIMEOUT, 10L);
curl_easy_setopt(curl, CURLOPT_RETRY_ON_FAILURE, 3L).

Exception Handling Black Technology

Catch packets are most afraid of encountering CAPTCHA interception, this time to offer a combination of punches:

1. expense or outlayipipgoDynamic Residential Proxy for Longer IP Survival Time
2. Randomize the User-Agent header
3. Control the frequency of requests, don't act like a hungry wolf.

// Disguise the browser request headers
struct curl_slist headers = NULL;
headers = curl_slist_append(headers, "User-Agent: Mozilla/5.0 (Windows NT 10.0)"); curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers); // fake browser request headers.
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

QA Frequently Asked Questions Demining

Q: What can I do if the agent can't connect?
A: Check the whitelist settings, firstipipgoSupport binding server IP or account password dual authentication

Q: What is the situation of returning 403 error?
A: 80% of the target site is enabled human verification, suggest switchingipipgoTry the mobile IP of

Q: How do I check if the proxy is in effect?
A: With this detection interface, the returned IP should be a proxy IP:

curl_easy_setopt(curl, CURLOPT_URL, "http://api.ipipgo.com/checkip");

Performance Optimization Tips

For multi-threaded acquisition, remember to give each thread a separate CURL handle. Use theipipgoThe Concurrency Package, which supports up to 5,000 concurrency, is even better with this configuration:

// Reuse connection pooling
curl_easy_setopt(curl, CURLOPT_FORBID_REUSE, 0L);
curl_easy_setopt(curl, CURLOPT_MAXCONNECTS, 100L); // multiplex connection pooling; // multiplex connection pooling; // multiplex connection pooling; // multiplex connection pooling.

Lastly, I would like to remind the old timers that you should not just look at the price when choosing an agency service.ipipgoExclusive IP quality detection system, automatic filtering of failed nodes, measured availability of 97% or more, which is the king of saving time and effort.