CS549 FTP (RMI + Sockets) — README

A tiny FTP-like system in Java.
Control channel: Java RMI for commands.
Data channel: a fresh TCP socket per file (like classic FTP).

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✨ Features

• pwd, cd, dir, ldir for remote/local navigation
• get and put with Passive (PASV) and Active (PORT) modes
• Works locally or across multiple EC2 instances
• Minimal configuration via CLI flags / properties
• Easy submission packaging (sources + jars + videos + rubric)

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🧠 Architecture (30-sec version)

• RMI (control): client ⇄ server for commands (fast, tiny messages).
• TCP (data): one ephemeral socket per transfer.

Passive (PASV)                           Active (PORT)
-----------------                        -----------------
Server: listen(data port S)              Client: listen(data port C)
Client: connect(S)                       Server: connect(C)
Direction: client→server connects        Direction: server→client connects

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🗂 Project Layout

ftpinterface/   RMI interfaces
ftpserver/      Server (builds ftpd.jar)
ftpclient/      Client (builds ftp.jar)

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🔧 Build

# from repo root
mvn clean package

# artifacts:
#   ftpserver/target/ftpd.jar
#   ftpclient/target/ftp.jar

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🚀 Run Locally (single machine)

Server (Terminal 1):

cd ftpserver/target
# bind passive data sockets to loopback for local testing
java -jar ftpd.jar --serverIp 127.0.0.1 --serverPort 1099

Client (Terminal 2):

cd ftpclient/target
java -jar ftp.jar --serverAddr localhost --serverPort 1099 --clientIp 127.0.0.1

Create a test tree next to where you start the server (e.g., root/hello.txt), then use commands below.

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☁️ Run Across Two EC2 Instances

Assumptions

• Same VPC; use private IPs (e.g., Server 172.31.25.252, Client 172.31.24.120).
• One security group for both is fine.

Security Group (simple demo setup)

• Inbound TCP from 172.31.24.120/32 (client) — enables PASV data + RMI.
• Inbound TCP from 172.31.25.252/32 (server) — enables PORT data.
  • Or add a self-reference rule (“this security group”) so any instance using the SG can talk to any other on all TCP ports.
• Keep SSH 22 from your public IP.

Start the server (on Server VM):

java -jar ftpd.jar --serverIp 172.31.25.252 --serverPort 1099

Start the client (on Client VM):

java -jar ftp.jar --serverAddr 172.31.25.252 --serverPort 1099 --clientIp 172.31.24.120

Tip:
--serverIp chooses which interface the server binds for PASV.
--clientIp chooses which interface the client binds for PORT (must be reachable by the server).

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⌨️ Client CLI — Commands

Command	Usage	Description
help	help	Show commands.
pwd	pwd	Print server’s current working directory.
cd	cd dir	Change server directory (.. up, . stay).
dir	dir	List files/dirs on server (within pwd).
ldir	ldir	List files in the client’s current folder.
pasv	pasv	Passive: server will listen for data; client will connect.
port	port	Active: client will listen for data; server will connect back.
get	get filename	Download file from server → client.
put	put filename	Upload file from client → server.
quit	quit	Exit the client.

Examples

Passive (firewall/NAT-friendly):

ftp> pasv
ftp> cd root
ftp> dir
ftp> get hello.txt
ftp> put upload.bin

Active:

ftp> port
ftp> get big.iso
ftp> put data.tar

Gotcha: get/put expect exactly two tokens. Run pasv/port on a separate line first.

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⚙️ Runtime Flags

• Server
  • --serverIp <IP>: interface to bind passive data sockets (e.g., 127.0.0.1, 172.31.x.x, or 0.0.0.0).
  • --serverPort <port>: RMI registry port (default in properties).
• Client
  • --serverAddr <host/IP>: where to find the server’s RMI registry (and the host to dial in PASV).
  • --serverPort <port>: RMI registry port.
  • --clientIp <IP>: interface to bind the client’s active-mode listener (PORT). Use client’s VPC IP or 0.0.0.0.

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✅ Testing Checklist (what to show in videos)

1. Navigation: pwd, cd into nested dirs, cd .. back up, dir at each level.
2. Passive transfers: pasv, get, put, verify with ldir and server listing.
3. Active transfers: port, get, put round-trip.
4. Security groups: show inbound rules and explain:
   • PASV: client connects to server data port (allow inbound on server).
   • PORT: server connects to client data port (allow inbound on client).
5. Integrity (optional):

   # run on both ends for a transferred file
   shasum hello.txt      # macOS
   # or
   sha1sum hello.txt     # Linux

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📦 Submission Packaging (exact format)

1. Build clean jars:

   mvn clean package

2. Create a submission folder named after you (e.g., Aayush_Rajesh_Jadhav) and put everything inside it.
3. Zip all sources (exclude target/, .git/, IDE files) into src.zip and place in that folder:

   zip -r src.zip . -x "*/target/*" ".git/*" ".idea/*"
   mv src.zip <Your_Name_Folder>/

4. Copy jars:

   cp ftpclient/target/ftp.jar  <Your_Name_Folder>/
   cp ftpserver/target/ftpd.jar <Your_Name_Folder>/

5. Add required videos (01-dir-nav.mp4, 02-passive.mp4, 03-active.mp4, 04-security-groups.mp4) and Rubric.pdf.
   (Optional) Add Test_Notes.txt describing what each video shows + IPs used.
6. Create the outer zip named after you that contains the folder named after you:

   cd <parent-of-Your_Name_Folder>
   zip -r Your_Name.zip Your_Name_Folder

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🧰 Troubleshooting Fast

• “GET/PUT: No mode set” → run pasv or port first.
• Active mode ConnectException: Connection refused
  Client listening on wrong interface. Start client with:

  --clientIp <client-private-ip>   # or 0.0.0.0

  Then port again and retry.
• Passive mode connection refused
  Start server with:

  --serverIp <server-private-ip>   # or 0.0.0.0

  Ensure SG allows inbound from client to server.
• Typed get hello.txt pasv → won’t run; pasv must be its own command first.

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🗒️ Example Sessions

Local / Passive

$ java -jar ftpd.jar --serverIp 127.0.0.1
$ java -jar ftp.jar  --serverAddr localhost --clientIp 127.0.0.1
ftp> pasv
ftp> cd root
ftp> dir
ftp> get hello.txt
ftp> ldir

EC2 / Active

# on server VM
$ java -jar ftpd.jar --serverIp 172.31.25.252 --serverPort 1099

# on client VM
$ java -jar ftp.jar --serverAddr 172.31.25.252 --serverPort 1099 --clientIp 172.31.24.120
ftp> port
ftp> get server.log
ftp> put upload.bin

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License

For course use (CS549).