# RFC Connection Setup

RFC is an alternative connection transport to HTTP. It works with any SAP system supported by the SAP NW RFC SDK. The RFC session is inherently stateful, so lock handles persist across calls without requiring HTTP stateful sessions.

## Prerequisites

### 1. SAP NW RFC SDK

Download from [SAP Support Portal](https://support.sap.com/en/product/connectors/nwrfcsdk.html) (requires S-user).

Extract to a local directory, e.g. `C:\nwrfcsdk\nwrfcsdk` (Windows) or `~/nwrfcsdk` (Linux/macOS).

### 2. Environment Variables

The SDK requires two shell-level environment variables. These **must** be set in the shell before starting Node.js — `.env` files do not work for this.

**Windows (PowerShell profile — persistent):**

Add to `$PROFILE` (usually `~\Documents\PowerShell\Microsoft.PowerShell_profile.ps1`):

```powershell
$env:SAPNWRFC_HOME = "C:\nwrfcsdk\nwrfcsdk"
$env:PATH = "C:\nwrfcsdk\nwrfcsdk\lib;$env:PATH"
```

**Windows (System Environment Variables — persistent):**

1. Open **System Properties** > **Environment Variables**
2. Add `SAPNWRFC_HOME` = `C:\nwrfcsdk\nwrfcsdk`
3. Append `C:\nwrfcsdk\nwrfcsdk\lib` to `PATH`

**Linux/macOS (bash/zsh profile — persistent):**

Add to `~/.bashrc` or `~/.zshrc`:

```bash
export SAPNWRFC_HOME=~/nwrfcsdk
export PATH=$SAPNWRFC_HOME/lib:$PATH
# Linux only:
export LD_LIBRARY_PATH=$SAPNWRFC_HOME/lib:${LD_LIBRARY_PATH:-}
```

### 3. @mcp-abap-adt/sap-rfc-lite Package

```bash
npm install @mcp-abap-adt/sap-rfc-lite
```

`@mcp-abap-adt/sap-rfc-lite` is a lightweight fork of the archived `node-rfc` package, containing only the API surface needed for ADT RFC connections. It is loaded dynamically at runtime — it is not a declared dependency.

Verify installation:

```bash
node -e "try { require('@mcp-abap-adt/sap-rfc-lite'); console.log('OK'); } catch(e) { console.log(e.message); }"
```

### 4. SAP Authorization

The SAP user needs `S_RFC` authorization for function module `SADT_REST_RFC_ENDPOINT`. See SAP Note 3569684.

## .env Configuration

For RFC connections, use two separate variables — one for authentication, one for connection type:

```env
SAP_URL=http://saphost:8000
SAP_USERNAME=DEVELOPER
SAP_PASSWORD=secret
SAP_CLIENT=100
SAP_AUTH_TYPE=basic
SAP_CONNECTION_TYPE=rfc
```

- `SAP_AUTH_TYPE` — authentication method (`basic` or `jwt`). RFC uses basic auth with username/password.
- `SAP_CONNECTION_TYPE` — transport layer (`http` or `rfc`).

## How It Works

1. `SAP_CONNECTION_TYPE=rfc` tells the server to create an `RfcAbapConnection` instead of HTTP
2. The connection calls SAP function module `SADT_REST_RFC_ENDPOINT` for every ADT request
3. The RFC session is inherently stateful — lock handles persist across calls
4. Host and system number are derived from `SAP_URL` (port 80XX -> system number XX)

## Troubleshooting

### "@mcp-abap-adt/sap-rfc-lite is not available"

SAP NW RFC SDK is not installed or not in PATH. Check:

```bash
echo $SAPNWRFC_HOME
node -e "require('@mcp-abap-adt/sap-rfc-lite')"
```

### "The specified module could not be found: sapnwrfc.node"

The native module exists but can't load SDK DLLs. Ensure `SAPNWRFC_HOME/lib` is in PATH **before** starting Node.js. Restart your terminal after setting variables.

### "RFC connection is not open"

The server failed to connect via RFC. Check SAP system availability, credentials, and `S_RFC` authorization.