Proxies or proxy servers help in anonymizing requests by assigning new online identities. For this reason, they are preferred during web scraping initiatives, which typically involve making numerous requests to a web server.
While creating a web scraper, it is important to automate repetitive processes such as requests, and this is where the cURL tool comes in. Incidentally, cURL can also be used to set up a proxy server, which is why this explanation article explores how to use cURL with proxies. But first, let’s understand what cURL is as well as what proxy servers are.
What is a Proxy Server?
A proxy is an intermediary computer that can serve a web client (user) or web server depending on the configuration and type. In cases where the proxy is meant to be used by the users, it routes all internet traffic – requests originating from the browser and responses sent by the server – through itself before sending it to the server or browser. As a result, it assigns all outgoing requests a new IP address, effectively anonymizing them. Client-side proxies also secure the connected computers, thus preventing cyberattacks.
On the other hand, a server-side proxy intercepts all incoming requests, thereby acting as an extra layer that prevents direct access to the server. Such a proxy offers numerous advantages. These include enhanced security, load balancing by distributing internet traffic among multiple servers, and storing static content (this increases the speed at which a browser renders/loads a webpage).
It is noteworthy that there are numerous types of proxies, including:
- Reverse proxies
- Forward proxies
- Transparent proxies
- HTTP proxies
- Residential proxies
- Datacenter proxies
- Rotating proxies
- Anonymous proxies and high anonymity proxies
What is cURL?
cURL, or client URL, is a free command-line tool available as an open-source software project that supports numerous internet protocols. It is therefore used to transfer data. The open-source project also includes an extensive library called libcurl, which is essentially an engine that powers thousands of services, applications, and tools that are used to perform internet data transfer.
There are numerous uses of cURL. These include:
- Data transfer
- Web scraping and data collection
- Uploading data to servers
- Setting up proxy servers and routing requests through them using the cURL with proxy commands
- Stipulating timeouts
- Testing and debugging URLs
- Establishing whether a web address is functional
- Sending and reading emails
- Automated username and password authentication in File Transfer Protocol (FTP) servers
- Verifying Secure Sockets Layer (SSL) certificates
This article will, however, focus on cURL’s utility in data collection and setting up proxies.
How to Use cURL with Proxies
As a command-line tool, cURL supports numerous functions. This, coupled with the fact that it supports multiple internet protocols such as HTTP, HTTPS, SOCKS (versions 4 and 4a), and SOCKS5, means that you can use cURL to set up and connect a browser to a proxy. To do this, simply establish the port you wish to use; for HTTP, the port is 8080, while for HTTPS, the port should be 423. Next, identify and define the IP address you would like your proxy to have. Then, type the cURL with proxy commands below (in our example, we will use http://example.com and https://example.com).
cURL with Proxy (HTTP Proxy)
To set up an HTTP proxy that uses the 192.168.0.1 IP address, key in the following:
curl -x 192.168.0.1:8080 http://example.com/
cURL with Proxy (HTTP Proxy)
To set up an HTTP proxy that uses the 192.168.0.1 IP address, key in the following:
curl -x 192.168.0.1:443 https://example.com/
cURL with Proxy (SOCKS5 Proxy)
Key in the following command on the cURL tool to set up a SOCKS5 proxy (this command locally resolves the hostname):
1 curl -x socks5h://proxy.example.com http://www.example.com/
2
3 curl –socks5-hostname proxy.example.com http://www.example.com/
To setup a SOCKS5 proxy whereby the hostname is not resolved locally, key in the following:
1 curl -x socks5://proxy.example.com http://www.example.com/
2
3 curl –socks5 proxy.example.com http://www.example.com/
cURL: Web Scraping and Proxies
Programmers can use cURL to set up a proxy server while simultaneously collecting data from websites such as the URL. In fact, cURL simply downloads the URL by default unless you specify otherwise. In this regard, the cURL with proxy commands above would simply download the URL via the proxy.
You can also use cURL to download files such as PDFs or HTML. However, to use this function along with the creation of proxies, you have to give cURL additional instructions. Check out one of the leading proxy providers on the market today and the article they wrote about using cURL with proxies.
Conclusion
cURL is a powerful, open-source software project that facilitates the transfer of data. Even so, programmers can use it to scrape data from websites as well as to set up and route traffic through proxy servers. However, it is noteworthy that while there are many types of proxies, cURL can only be used to set up proxy servers that are based on internet protocols. Examples include HTTP, HTTPS, and SOCKS.
