Ultraviolet Proxy

When choosing a proxy through which to connect to Skype, pay attention to the stability of its work, the level of anonymity and low load that exceeds the final speed of the connection. Launch the Skype application and open the context menu "Tools". Through the "Advanced" tab, go to "Connection" to open the "Change settings" tab. Here, in the special form, specify the IP address and port, and then click "Save" and restart Skype.

Checking data integrity in the User Datagram Protocol (UDP) can be challenging, as UDP is a connectionless protocol and does not provide built-in mechanisms for ensuring data integrity, such as error detection or correction. However, there are several methods to check data integrity in UDP:

1. Checksum: UDP uses a simple checksum mechanism to detect errors in transmitted data. The sender calculates the checksum of the UDP header and data using a cyclic redundancy check (CRC) algorithm. The checksum value is then included in the UDP header and transmitted along with the data. Upon receiving the data, the receiver calculates the checksum of the received data and compares it to the checksum value in the UDP header. If the values do not match, the receiver can assume that an error has occurred during transmission. However, this checksum mechanism does not protect against all types of errors or attacks.

2. Application-level checksum: Since UDP does not provide robust error detection, many applications implement their own checksum or hash functions at the application layer to verify data integrity. For example, when transmitting sensitive data, an application can calculate a hash value of the data using an algorithm like MD5 or SHA-1 and include the hash value in the transmitted data. The receiver can then calculate the hash value of the received data and compare it to the included value to ensure data integrity.

3. Secure UDP: To ensure data integrity and security, you can use a secure version of UDP, such as Datagram Transport Layer Security (DTLS) or Secure Real-time Transport Protocol (SRTP). These protocols provide authentication, encryption, and integrity checks to protect data during transmission.

4. Application-level protocols: Some applications use specific protocols that provide additional data integrity checks, such as the Real-time Transport Protocol (RTP) for audio and video streaming. RTP includes sequence numbers and timestamps to help detect lost or out-of-order packets and ensure proper playback.

In summary, checking data integrity in UDP can be achieved through various methods, such as using the built-in checksum mechanism, implementing application-level checksums or hashes, employing secure UDP protocols, or utilizing application-level protocols that provide additional data integrity checks.

In the context of a proxy server, the term "host" refers to the IP address or domain name of the proxy server itself. The host is the destination where your internet traffic is routed through when you use a proxy server. When you configure your web browser or software to use a proxy, you're specifying the host (proxy server address) and the port number to connect to the proxy server.

The proxy server then forwards your web requests to the actual destination (e.g., a website) and returns the response back to you. This process allows the proxy server to act as an intermediary between you and the internet, potentially providing benefits such as anonymity, access to restricted content, or improved performance.

To view the proxy settings on your computer, you can follow these steps depending on the operating system you are using:

For Windows:
- Press the Windows key + R to open the Run dialog box.
- Type "inetcpl.cpl" (without quotes) in the Run dialog box and press Enter.
- In the Internet Properties window, go to the Connections tab.
- Click on the "LAN settings" button.
- In the LAN Settings window, you will see the proxy server settings. If there is a checkmark in the "Use a proxy server for your LAN" box, it means you are using a proxy server.

For macOS:
- Click on the Apple menu in the top-left corner of your screen.
- Select "System Preferences" from the dropdown menu.
- Click on "Network" in the System Preferences window.
- Select the network connection you are using (e.g., Wi-Fi, Ethernet) from the left pane.
- Click on the "Advanced" button.
- In the Advanced window, go to the "Proxies" tab to view the proxy settings.

To keep only unique external links while scraping with Scrapy, you can use a set to track the visited external links and filter out duplicates. Here's an example spider that demonstrates how to achieve this:

import scrapy
from urllib.parse import urlparse, urljoin

class UniqueLinksSpider(scrapy.Spider):
    name = 'unique_links'
    start_urls = ['http://example.com']  # Replace with the starting URL of your choice
    visited_external_links = set()

    def parse(self, response):
        # Extract all links from the current page
        all_links = response.css('a::attr(href)').extract()

        for link in all_links:
            full_url = urljoin(response.url, link)

            # Check if the link is external
            if urlparse(full_url).netloc != urlparse(response.url).netloc:
                # Check if it's a unique external link
                if full_url not in self.visited_external_links:
                    # Add the link to the set of visited external links
                    self.visited_external_links.add(full_url)

                    # Yield the link or process it further
                    yield {
                        'external_link': full_url
                    }

        # Follow links to other pages
        for next_page_url in response.css('a::attr(href)').extract():
            yield scrapy.Request(url=urljoin(response.url, next_page_url), callback=self.parse)

- visited_external_links is a class variable that keeps track of the unique external links across all instances of the spider.
- The parse method extracts all links from the current page.
- For each link, it checks if it is an external link by comparing the netloc (domain) of the current page and the link.
- If the link is external, it checks if it is unique by looking at the visited_external_links set.
- If the link is unique, it is added to the set, and the spider yields the link or processes it further.
- The spider then follows links to other pages, recursively calling the parse method.

Remember to replace the start_urls with the URL from which you want to start scraping.