Web Server

Web servers accept HTTP requests and return responses to clients.

What is a Web Server?

A web server is software that:

Listens on a network port (usually 80 for HTTP, 443 for HTTPS)
Receives HTTP requests from clients
Processes requests or serves static files
Sends HTTP responses back to clients
Handles multiple concurrent connections

Popular Web Servers

Nginx

High-performance, lightweight web server

Used as web server, reverse proxy, load balancer
Event-driven architecture
Efficient resource usage
Configuration: /etc/nginx/nginx.conf

# Install Nginx
sudo apt install nginx

# Start Nginx
sudo systemctl start nginx
sudo systemctl enable nginx

# Check status
sudo systemctl status nginx

Apache

Traditional web server with modular design

Long history and wide adoption
Process-driven architecture
Extensive module ecosystem
Configuration: /etc/apache2/apache2.conf

# Install Apache
sudo apt install apache2

# Enable modules
sudo a2enmod proxy
sudo a2enmod rewrite

# Restart Apache
sudo systemctl restart apache2

HTTP Request/Response Cycle

Client Request:
GET /index.html HTTP/1.1
Host: example.com
User-Agent: Mozilla/5.0

Server Response:
HTTP/1.1 200 OK
Content-Type: text/html
Content-Length: 1234

<html>...</html>

Common HTTP Methods

GET - Retrieve resource
POST - Submit data
PUT - Update resource
DELETE - Remove resource
PATCH - Partial update
HEAD - Like GET but no body
OPTIONS - Describe communication options

Serving Static Files

# Nginx configuration
server {
    listen 80;
    server_name example.com;

    root /var/www/html;
    index index.html index.htm;

    location / {
        try_files $uri $uri/ =404;
    }
}

Virtual Hosts

# Multiple sites on one server
server {
    listen 80;
    server_name site1.com;
    root /var/www/site1;
}

server {
    listen 80;
    server_name site2.com;
    root /var/www/site2;
}

Common HTTP Status Codes

2xx Success
- 200: OK
- 201: Created
- 204: No Content
3xx Redirection
- 301: Moved Permanently
- 302: Found (temporary redirect)
- 304: Not Modified
4xx Client Error
- 400: Bad Request
- 401: Unauthorized
- 403: Forbidden
- 404: Not Found
5xx Server Error
- 500: Internal Server Error
- 502: Bad Gateway
- 503: Service Unavailable

Performance Optimization

# Gzip compression
gzip on;
gzip_types text/plain text/css text/javascript;
gzip_min_length 1000;

# Caching
location ~* \.(jpg|jpeg|png|gif|ico|css|js)$ {
    expires 1y;
    add_header Cache-Control "public, immutable";
}

# Connection pooling
keepalive_timeout 65;

Logging

# Log HTTP requests
log_format main '$remote_addr - $remote_user [$time_local] '
                '"$request" $status $body_bytes_sent '
                '"$http_referer" "$http_user_agent"';

access_log /var/log/nginx/access.log main;
error_log /var/log/nginx/error.log warn;

Health Checks

# Check if web server is running
curl -I http://localhost

# Get response code
curl -s -o /dev/null -w "%{http_code}" http://localhost

# Monitor logs
tail -f /var/log/nginx/access.log

Best Practices

Use Nginx for high traffic scenarios
Keep software updated
Configure proper logging
Use HTTPS/SSL
Implement proper security headers
Monitor performance metrics
Use appropriate timeouts
Implement rate limiting
Keep configurations DRY (Don't Repeat Yourself)
Document custom configurations

Web Server

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