Telnet & TCP

Both are byte-stream protocols. D.device.sendTelnetCommand handles Telnet-style line-buffered command/response; D.device.sendTCPCommand is a lower-level send-bytes-and-collect-bytes primitive for devices that speak a custom text or binary protocol.

Telnet

D.device.sendTelnetCommand({
    command: 'show interfaces',
    username: 'admin',
    password: 'secret',
    shell_prompt: '#',
    login_prompt: 'login:',
    password_prompt: 'Password:',
    timeout: 5000
}, function (output, error) {
    if (error) return D.failure(D.errorType.RESOURCE_UNAVAILABLE);
    console.log(output);
});

Key options:

• shell_prompt — the runner waits for this string before sending command (and before returning).
• login_prompt / password_prompt — if these are set, the runner sends username / password when they appear.
• timeout — ms; on zero output within this window, the runner gives up.

Telnet sends credentials in cleartext. Prefer SSH when the device supports it.

Raw TCP

D.device.sendTCPCommand({
    command: '?\r\n',
    port: 4242,
    timeout: 500,
    keepAlive: false,
    encoding: 'utf8'
}, function (output, error) {
    if (error) return D.failure(D.errorType.RESOURCE_UNAVAILABLE);
    console.log(output);
});

Key options:

• command — the exact string to write on the socket. Include terminators (\r\n, \n, NUL) if the protocol needs them.
• port — defaults to 23 (Telnet); override for custom services.
• timeout — the runner waits this many ms after the last byte received, then closes and returns.
• keepAlive — if true the socket stays open until the timeout expires; useful for protocols that send multiple response chunks.
• encoding — how to decode the returned bytes. Set to 'binary' for non-text protocols and parse the Buffer yourself.

Binary protocols

For pure binary exchanges, set encoding: 'binary', send raw bytes in command, and decode the output (which comes back as a binary string in that mode):

D.device.sendTCPCommand({
    command: String.fromCharCode(0x01, 0x02, 0x03),
    port: 1234,
    encoding: 'binary',
    timeout: 200
}, function (output, error) {
    if (error) return D.failure(D.errorType.RESOURCE_UNAVAILABLE);
    var bytes = [];
    for (var i = 0; i < output.length; i += 1) bytes.push(output.charCodeAt(i));
    // ... inspect bytes
});

Error handling

D.device.sendTelnetCommand({ ... }, function (output, error) {
    if (error) {
        if (error.code === 'ECONNREFUSED') return D.failure(D.errorType.RESOURCE_UNAVAILABLE);
        if (error.code === 'ETIMEDOUT')   return D.failure(D.errorType.TIMEOUT_ERROR);
        if (error.code === 'AUTHENTICATION_FAILED') return D.failure(D.errorType.AUTHENTICATION_ERROR);
        return D.failure(D.errorType.GENERIC_ERROR);
    }
});

Related API

• D.device.sendTelnetCommand
• D.device.sendTCPCommand