re: org.apache.tools.ant.taskdefs.optional.net.TelnetTask

The two instances of while-loops currently written like this

while (windowStart++ < 0 
    || !sb.substring(windowStart).equals(s)) {

are wrong. The increment happens before taking the substring. Changing it to this

while (windowStart < 0 
    || !sb.substring(windowStart).equals(s)) {
    windowStart++;

makes it clearer when windowStart is incremented, and makes the code correct. 

Debugging the code while doing the classic case, looking for "ogin:" before typing the username demonstrates that the comparison will be "ogin:" to "gin:" at the iteration when it should break out of the loop, making the loop invariant true.