Implement a WebSocket Handshake and Frame Parser

Write a C program that documents the WebSocket handshake and parses a WebSocket frame. Show key generation, accept calculation, and frame decode.

Requirements:

• Generate a random 16-byte nonce and Base64-encode it to create Sec-WebSocket-Key
• Compute Sec-WebSocket-Accept by concatenating the key with the GUID, computing SHA-1, and Base64-encoding
• Print the client handshake request showing the Upgrade and Sec-WebSocket-Key headers
• Print the server handshake response showing the 101 status and Sec-WebSocket-Accept
• Define the WebSocket frame structure (FIN, opcode, MASK, length, masking key, payload)
• Parse a sample frame byte array and extract each field
• If the frame is masked, show how to unmask the payload with XOR
• Print a breakdown of each frame field with printf