What causes the Broken Pipe Error

Question

I know that broken pipe error is thrown when the socket on the peer side is closed   But  in my test I have noted that an immediate  send  call on this side when the peer side is closed doesn t always lead to a broken pipe error   E g    After closing the socket on peer side  I have tried clean closing by calling close and also abnormal closing by killing the peer   if I try to send 40 bytes  then I don t get a broken pipe  but  if I try to send 40000 bytes then it immediately gives broken pipe error   What exactly causes broken pipe and can it s behavior be predicted

User · Answer

When peer close  you just do not know whether it just stop sending or both sending and receiving Because TCP allows this  btw  you should know the difference between close and shutdown   If peer both stop sending and receiving  first you send some bytes  it will succeed  But the peer kernel will send you RST  So subsequently you send some bytes  your kernel will send you SIGPIPE signal  if you catch or ignore this signal  when your send returns  you just get Broken pipe error  or if you don t   the default behavior of your program is crashing

User · Answer

It can take time for the network close to be observed - the total time is nominally about 2 minutes  yes  minutes   after a close before the packets destined for the port are all assumed to be dead   The error condition is detected at some point   With a small write  you are inside the MTU of the system  so the message is queued for sending   With a big write  you are bigger than the MTU and the system spots the problem quicker   If you ignore the SIGPIPE signal  then the functions will return EPIPE error on a broken pipe - at some point when the broken-ness of the connection is detected

User · Answer

The current state of a socket is determined by  keep-alive  activity  In your case  this is possible that when you are issuing the send call  the keep-alive activity tells that the socket is active and so the send call will write the required data  40 bytes  in to the buffer and returns without giving any error   When you are sending a bigger chunk  the send call goes in to blocking state   The send man page also confirms this      When the message does not fit into the send buffer of the socket  send   normally blocks  unless the socket has been placed in non-blocking I O mode  In non-blocking mode it would return EAGAIN in this case   So  while blocking for the free available buffer  if the caller is notified  by keep-alive mechanism  that the other end is no more present  the send call will fail   Predicting the exact scenario is difficult with the mentioned info  but I believe  this should be the reason for you problem

User · Answer

Maybe the 40 bytes fits into the pipe buffer  and the 40000 bytes doesn t   Edit   The sending process is sent a SIGPIPE signal when you try to write to a closed pipe  I don t know exactly when the signal is sent  or what effect the pipe buffer has on this  You may be able to recover by trapping the signal with the sigaction call

User · Answer

We had the Broken Pipe error after a new network was put into place  After ensuring that port 9100 was open and could connect to the printer over telnet port 9100  we changed the printer driver from  HP  to  Generic PDF   the broken pipe error went away and were able to print successfully    RHEL 7  Printers were Ricoh brand  the HP configuration was pre-existing and functional on the previous network

[c] What causes the Broken Pipe Error?

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