Debugging TDS

Enable debugging in your config.

var config = {
    user: '...',
    password: '...',
    server: 'localhost',
    database: '...',
    debug: true // <--- here
}

Attach debug event handler to connection pool.

const pool = new sql.ConnectionPool(config)
pool.on('debug', (connection, message) => {
    console.log(message)
})
pool.connect()

It logs all TDS traffic between your app and SQL Server. Logs should look like this:

connected to 192.168.5.130:1433

Sent
  type:0x12(PRELOGIN), status:0x01(EOM), length:0x002F, spid:0x0000, packetId:0x01, window:0x00
  0000  00001A00 06010020 00010200 21000103 00220004 04002600 01FF0000 00010001  ....... ....!... ."....&. ........
  0020  02000000 000000  .......
  PreLogin - version:0.0.0.1 1, encryption:0x02(NOT_SUP), instopt:0x00, threadId:0x00000000, mars:0x00(OFF)
State change: Connecting -> SentPrelogin

Received
  type:0x04(TABULAR_RESULT), status:0x01(EOM), length:0x002B, spid:0x0000, packetId:0x01, window:0x00
  0000  00001A00 06010020 00010200 21000103 00220000 04002200 01FF0B00 08340000  ....... ....!... ."....". .....4..
  0020  020000  ...
  PreLogin - version:11.0.8.52 0, encryption:0x02(NOT_SUP), instopt:0x00, threadId:0x00000000, mars:0x00(OFF)

And many more of similar lines.

IMPORTANT: These logs contains binary serialized credentials to your SQL Server! Always change your password before you send those logs to anyone.

NOTE: Debugging only work with default Tedious driver.