# j3270

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An **x3270-aligned IBM 3270 mainframe terminal emulator** written in pure Java. Designed for high compatibility with IBM z/OS, z/VM, CMS, and TSO systems over TN3270 and TN3270E.

---

## 🚀 Quick Download & Run

### Latest Standalone JAR
You can download the ready-to-run executable JAR directly from the releases or CI builds:

- **[Download Latest Tagged Release (`j3270.jar`)](https://git.hugfreevikings.wtf/rudi/j3270/releases)**
- **[Latest Nightly CI Artifacts](https://git.hugfreevikings.wtf/rudi/j3270/actions)** (Download under the latest successful workflow run)

### Running `j3270`
Requires **Java 11 or higher** (Java 11, 17, 21+):

```bash
# Launch interactive GUI
java -jar j3270.jar

# Connect to TLS/SSL mainframe with custom port
java -jar j3270.jar -s mainframe.example.com 992
# Or using standard x3270 L: prefix
java -jar j3270.jar L:mainframe.example.com:992

# Connect via Plain TN3270 (Non-E)
java -jar j3270.jar -P mainframe.example.com 23
# Or using standard x3270 P: prefix
java -jar j3270.jar P:mainframe.example.com:23

# Connect with unverified/self-signed certificate verification bypass
java -jar j3270.jar --tls --insecure mainframe.example.com 992

# Launch with custom configuration file
java -jar j3270.jar -c config.ini

# Launch directly from source runner
./run.sh
```

---

## ✨ Features

- **TN3270 & TN3270E Protocol Support**: RFC 2355 compliant state machine, negotiation, Device-Type query, plain TN3270 fallback, and SSL/TLS encryption.
- **SSL/TLS Security**:
  - Encrypted TN3270 over TLS connections on standard port `992` or custom ports.
  - Interactive certificate verification prompt for self-signed or untrusted certificates with fingerprint, subject, issuer, and validity inspection.
  - Optional unverified/insecure mode for testing and headless scripting.
- **IND$FILE File Transfer**: Full support for both **CUT** and **DFT (DDM)** high-speed structured field transfers with ASCII/binary translation, CRLF handling, and recfm/lrecl formatting for TSO, VM/CMS, and CICS.
- **z/VM & Line-Mode Support**: Proper SSCP-LU and unformatted line handling (`CP TERM CONMODE 3270` supported).
- **APL & Graphic Escape**: Comprehensive box-drawing and math symbol character rendering.
- **Terminal Models**:
  - Model 2 (24x80)
  - Model 3 (32x80)
  - Model 4 (43x80)
  - Model 5 (27x132)
- **Zero-Dependency Core**: Modular architecture separated into:
  - `lib3270j`: Reusable Java 3270 protocol, data stream parser, charset translation, and telnet state machine.
  - `j3270`: Desktop Swing user interface and session management.

---

## 🛠️ Building from Source

### Standalone Build (No Gradle Required)
The project includes self-contained, portable build scripts:

```bash
# Build executable JAR in 2 seconds:
sh ./build_all.sh

# Run all 56 automated unit tests in ~500ms:
sh ./test_all.sh
```

The resulting standalone JAR is created at `build/j3270.jar`.

### Gradle Build (Optional)
```bash
./gradlew build
./gradlew test
```

---

## 🤝 Contributing

Contributions and issue reports are welcome! Please feel free to open a bug report or feature request via the Gitea issue tracker.

---

## 📜 Acknowledgements

- [x3270](https://x3270.miraheze.org/wiki/Main_Page) — Reference C implementation and protocol specifications
- [Antigravity](https://antigravity.google/)
- Claude Opus 4.6
- Gemini 3.1 Pro
- Gemini 3.7 Flash
- Gemma4 12B and 26B
- GPT-OSS 120B
- Qwen3 4B and 32B