📁 GoDrop - Simple TCP File Receiver in Go

GoDrop is a lightweight TCP server written in Go that receives files over a custom TCP protocol and stores them in a local directory. Perfect for learning low-level networking and file transfer mechanics.

🚀 Features

• Accepts incoming TCP connections on 127.0.0.1:8080
• Handles multiple clients concurrently using goroutines
• Supports basic header-based protocol (filename and filesize)
• Displays a real-time progress bar while receiving files
• Graceful shutdown on SIGINT / SIGTERM (e.g., Ctrl+C)
• Automatically stores received files in the goDropped/ folder with a timestamped, IP-prefixed filename
• Max file size limit of 10 MB

📦 Protocol Format

Client should send headers followed by the file bytes:

filename: my_file.txt
filesize: 12345

[RAW FILE BYTES...]

• Headers must be followed by a blank line (\n) before the file data begins.
• filename is the original file name.
• filesize is the number of bytes to be read from the stream after the headers.

📊 Progress Bar in Action

While receiving a file, GoDrop now shows a visual progress bar in the terminal:

Receiving: [##########----------] 50.00%

This updates in real time as the server writes chunks to disk.

🛠️ Running the Server

Make sure you have Go installed. Then run:

go run main.go

Server will start listening on 127.0.0.1:8080

You should see:

Serving on PORT 8080
START Reading incoming message...
START Reading file content from my_file.txt of size 12345
Receiving: [####################] 100.00%
File received successfully.
Saved my_file.txt in goDropped/1716271874_127.0.0.1_my_file.txt successfully

🧪 Example Client (Using netcat)

You can test the server using nc (netcat) as a basic client:

(
  echo -e "filename: test.txt\nfilesize: $(wc -c < test.txt)\n\n";
  cat test.txt
) | nc 127.0.0.1 8080

Make sure test.txt exists in the same directory.

📁 Output

Received files will be stored in the goDropped/ directory with names like:

goDropped/1716271874_127.0.0.1_test.txt

This includes a Unix timestamp and sender's IP to avoid collisions.

🧹 Graceful Shutdown

The server listens for system signals like SIGINT and SIGTERM to shut down cleanly:

^C
Server is being closed due to signal: interrupt
Stopping accepting connections...
Server shutdown

🧯 Error Handling

• Malformed headers? You'll get a 400 Bad Request.
• File too big? The server politely declines.
• Disk I/O errors? They're logged, and the connection is safely dropped.

🧰 Tech Stack

• 🐹 Go (Golang)
• 📡 TCP Sockets
• 🧵 Goroutines
• 💾 os, bufio, net, and time packages

📜 License

MIT License. Do whatever you want. Just don't claim you wrote it first 😉.

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Enjoy dropping files the Go way! 🚀