ECHO mode is one of the many ways the YF client connects to the servers. This mode uses ICMP ECHO packets, also known as ping packets, for tunneling.
In some places you might not be able to fully access Internet services, but you may still be able to use the "ping" utility. If this is the case, ICMP ECHO mode is what you need to get connected.
ECHO mode is not available on all platforms, due to the fact that "raw sockets" are not available in pure Java. In order to access low-level socket functionality we need to use the so-called JNI (java native-code interface), and this means that we need to ship pre-compiled binary code as a dynamic link library. Also, because of the privacy sensitive nature of raw sockets, modern operating systems require applications to run with elevated privileges in order to use raw sockets (a prerequisite for ECHO mode). This means that on Windows systems you'll need to run as administrator, and on Linux systems you'll need to run as root. It won't work with our Android app or on Mac OSX.
You'll need Windows or Linux on a PC, it won't work on any other systems (including Mac OS X and Android -- sorry).
If you are running on Windows, details about running the YF client as administrator can be found here. You must run as administrator or ECHO mode won't work.
If you are running on Linux, you'll need to find a way to ensure that the YF client has root privileges. A simple method would be to SSH to localhost using the root login.
Once you are sure you are running as administrator, click "Configure", then click the Wizard button on the top right. Enable ECHO mode for server search, disable all modes you don't want to test, then run the search. Or simply choose ECHO connection mode (the port does not matter). All our servers support ECHO mode.
Check the message log; is there a message about insufficient privileges? This would mean that you are not running as administrator.
If it still doesn't work, are you sure you can ping hosts on the Internet? Open a command shell, then try "ping 18.104.22.168" or some other IP that is guaranteed to respond. Do you get replies? If not, you cannot use ECHO mode.