function onClientPacket(event) {
    var packet = event.getPacket();
    switch (packet.id()) {
        case ID_PLAYER_TEXT:
            {
                var text = packet.text;
                if (text === "/sell") {
                    var newtradepacket = event.createPacket(ID_REQUESTTRADE);
                    //look in scripthelp.js for what a requesttrade packet contains, set them manually:
                    //newtradepacket.name = "other"; (example)
                    event.sendToServer(newtradepacket);
                }
            }
    }
}