@jcaron unfortunately, there is any method with the stdin and I haven't found any way to interact directly with the telnet server.
My previous implementation used the UART, but then I realized that I was able to read from Telnet, but no way to type anything. Also, the telnet connection was quite slow and unreliable for some reason (time out when login/password). With stdin it works much better, but not typing anything will block the application forever.