On 22 Apr 2013, at 15:10, Xiangrong Fang wrote: > > 1) fpsend() just pass data to the OS's socket layer without try to determine > if the connection is still alive, right?
I suppose, but there exists an error code that might come in handy: ENotConn (see http://linux.die.net/man/2/send), which is returned by send(). > > 2) is it normal that in BLOCK mode, recv returns 0? i.e. if I receive a 0 > from fprecv(), I can say that the connection is closed by the other end (if > there is no detectable socketerror), right? > Yes, if recv() return 0, it mens the client disconnected. If it returns -1, errno will be set. From http://linux.die.net/man/2/recv (see `return value`): "These calls return the number of bytes received, or -1 if an error occurred. The return value will be 0 when the peer has performed an orderly shutdown." Note that even in non-blocking mode, 0 means the socket is closed. If you received no data yet, you will get -1 as a return value and errno will be set to EAgain of EWouldBlock (see the link above). Does this help or am I completely talking besides the point? -- Ewald
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