Client and server now include a 1-byte stream ID alongside the 16-byte session ID (17 bytes total) so multiple logical streams can be multiplexed per session. Client: propagate streamID through connection helpers and send sessionID+streamID when establishing DTLS connections; default stream 0 for the first connection and subsequent goroutines pass incremental stream IDs. Server: read 17-byte header, split into sessionID and streamID, and track connections as streamEntry {id, conn} rather than a plain conn slice. AddConn/RemoveConn signatures updated to accept stream IDs; new logic evicts existing connection with the same stream ID. backendReaderLoop uses a local round-robin index (removed atomic usage) and closes connections on write errors. Also adjusted per-stream read deadlines and cleaned up connection closing in Cleanup().