POLLRDHUP (since Linux 2.6.17)
Stream socket peer closed connection, or shut down writing half of connection. The _GNU_SOURCE feature test macro must be defined (before including any header files) in order to obtain this definition.

EPIPE
This socket was connected but the connection is now broken. In this case, send generates a SIGPIPE signal first; if that signal is ignored or blocked, or if its handler returns, then send fails with EPIPE.

tcp_disconnect.py This program easily translates to C & Java. By TCP rules, the only way for a server program to know if a client has disconnected, is to try to read from the socket. Specifically, if select() says there is data, but recv() returns 0 bytes of data, then this implies the client has disconnected. But a server program might want to confirm that a tcp client is still connected without reading data. For example, before it performs some task or sends data to the client. This program will demonstrate how to detect a TCP client disconnect without reading data. The method to do this: 1) select on socket as poll (no wait) 2) if no recv data waiting, then client still connected 3) if recv data waiting, the read one char using PEEK flag 4) if PEEK data len=0, then client has disconnected, otherwise its connected. Note, the peek flag will read data without removing it from tcp queue. To see it in action: 0) run this program on one computer 1) from another computer, connect via telnet port 12345, 2) type a line of data 3) wait to see it echo, 4) type another line, 5) disconnect quickly, 6) watch the program will detect the disconnect and exit. I hope this is helpful to someone. John Masinter, 17-Dec-2008. """