Silent quit of telnet servers leading to clients waiting forever

[jerrytesting]

After telnet clients connect with telnet servers, clients stay blocking until receiving timeout from servers. So when the telnet server interrupts unexpectedly, the server should give an alert to clients. However, telnet servers often quit silently, thereby leading to clients waiting forever.

This bug can be reproduced when one telnet client connects with one telnet server, and then the telnet server unexpectedly quits. Then we could found that the client will be stuck there and cannot stop until CPU resources run out.