In some cases, you may need to build your own HTTP proxy server to better control and manage network traffic. Here is a detailed tutorial on how to build a simple HTTP proxy server on a Linux system.

preliminary

Before you begin, you'll need to prepare the following tools and resources:

1. A server running Linux (e.g. Ubuntu, CentOS, etc.)
2. SSH client (e.g. PuTTY or terminal)
3. Squid (an open source proxy server software)

Step 1: Update the system package

First, connect to your Linux server via SSH and update the system packages:

sudo apt-get update && sudo apt-get upgrade -y # for Debian/Ubuntu
sudo yum update -y # for CentOS/RHEL

Step 2: Install Squid

Install Squid using the package manager:

sudo apt-get install squid -y # for Debian/Ubuntu
sudo yum install squid -y # for CentOS/RHEL

Step 3: Configure Squid

Squid's configuration file is located at `/etc/squid/squid.conf`. Use a text editor (e.g. vim, nano) to edit this file:

sudo nano /etc/squid/squid.conf

In the configuration file, you can configure it as needed. Here are some common configuration items:

# Allow all network access
http_access allow all

# Set the proxy server port (default 3128)
http_port 3128

# Setting the cache directory and size
cache_dir ufs /var/spool/squid 100 16 256

# Setting the cache log file
cache_log /var/log/squid/cache.log
access_log /var/log/squid/access.log

Save and close the configuration file.

Step 4: Initialize the cache directory

Before running Squid for the first time, you need to initialize the cache directory:

sudo squid -z

Wait for the initialization to complete.

Step 5: Start Squid

Start the Squid proxy server using the following command:

sudo systemctl start squid

You can also check the status of Squid to make sure it is running using the following command:

sudo systemctl status squid

Step 6: Setting up boot-up

In order to have Squid run automatically at system startup, you can set up a boot self-start with the following command:

sudo systemctl enable squid

Step 7: Configure the Firewall

If your server has a firewall enabled, you need to open the port used by Squid (3128 by default):

sudo ufw allow 3128/tcp # For UFW firewalls
sudo firewall-cmd --permanent --add-port=3128/tcp # For Firewalld
sudo firewall-cmd --reload # Reload Firewall Configuration

Step 8: Test the proxy server

On the client device, you need to set the IP address and port of the proxy server. Here's how to configure the proxy on macOS and Windows devices:

Configuring the agent on macOS

1. Open System Preferences and click Network.
2. Select the network connection you are using (e.g. Wi-Fi) and click Advanced.
3. In the Proxy tab, check Web Proxy (HTTP) and Secure Web Proxy (HTTPS).
4. Enter the IP address and port of the proxy server (default is 3128).
5. Click "OK" to save the settings and close the window.

Configuring the Agent on Windows

1. Open "Settings" and click "Network and Internet".
2. Select the Proxy tab.
3. In the "Manually set up a proxy" section, enable the "Use a proxy server" option.
4. Enter the IP address and port of the proxy server (default is 3128).
5. Click the "Save" button.

Advanced Configuration

Squid provides a rich set of configuration options for advanced configuration as needed:

Setting up Access Control

You can restrict which clients can access the proxy server by configuring access control lists (ACLs):

# Allow access to specific IP address ranges
acl allowed_ips src 192.168.1.0/24
http_access allow allowed_ips

# Deny all other access
http_access deny all

Enable authentication

You can configure Squid to require clients to authenticate:

# Install the authentication module
sudo apt-get install apache2-utils # for Debian/Ubuntu
sudo yum install httpd-tools # for CentOS/RHEL

# Creating a user password file
sudo htpasswd -c /etc/squid/passwd myuser

# Configuring Squid to use authentication
auth_param basic program /usr/lib/squid/basic_ncsa_auth /etc/squid/passwd
auth_param basic children 5
auth_param basic realm Squid proxy-caching web server
auth_param basic credentialsttl 2 hours
acl authenticated proxy_auth REQUIRED
http_access allow authenticated
http_access deny all

caveat

There are a few things to keep in mind when using a proxy server:

1. Security:Make sure your proxy server configuration is secure from unauthorized access.
2. Performance:Proxy servers may affect network performance, especially under high load.
3. Logging:Regularly check and clean up log files to avoid taking up too much disk space.

summarize

With the above steps, you can build a simple HTTP proxy server on your Linux system to control and manage network traffic, protect privacy, and even speed up network access. Squid is a powerful and flexible proxy server software, whether it is intended for personal use or a small network environment.

I hope this article has helped you better understand and use HTTP proxy servers. I wish you a smooth journey in the online world!