How to convert socket input to String in TcpInboundGateway?

I have a TcpInboundGateway receiving content from a socket. A telnet connection already works fine, exception one thing: I'm getting the decimal representation of the input, instead of real letters.

@MessageEndpoint
public class MyEndpoint {
    @ServiceActivator(inputChannel = "chan")
    public String hello(String input) throws Exception {
        System.out.println("Server returning: " + input);
        return "Server returning: " + input;
    }

    @Bean
    public MessageChannel chan() {
        return new DirectChannel();
    }

    //@Bean TcpInboundGateway
    //@Bean TcpConnectionFactoryFactoryBean "server"
}

Now, when I use eg a telnet connection, the input string received at the ServiceActivator is like "120,120,120" instead of "xxx" (which is decimal of ascii code).

How can I tell the gateway to automatically convert the decimal to utf-8 letters?