Java NIO What does IOException Broken pipe mean

Question

For some of my Java NIO connections  when I have a SocketChannel write ByteBuffer  call  it throws an IOException   Broken pipe    What causes a  broken pipe   and  more importantly  is it possible to recover from that state  If it cannot be recovered  it seems this would be a good sign that an irreversible problem has occurred and that I should simply close this socket connection  Is that a reasonable assumption  Is there ever a time when this IOException would occur while the socket connection is still being properly connected in the first place  rather than a working connection that failed at some point    On a side note  is it wise to always call SocketChannel isConnected   before attempting a SocketChannel write    and if so  can I also assume that the connection is  broken  and should be closed if both SocketChannel isConnected   and SocketChannel isConnectionPending   are both false   Thanks

User · Answer

You should assume the socket was closed on the other end. Wrap your code with a try catch block for IOException.

You can use isConnected() to determine if the SocketChannel is connected or not, but that might change before your write() invocation finishes. Try calling it in your catch block to see if in fact this is why you are getting the IOException.

User · Answer

What causes a  broken pipe   and more importantly  is it possible to recover from that state    It is caused by something causing the connection to close    It is not your application that closed the connection  that would have resulted in a different exception    It is not possible to recover the connection   You need to open a new one      If it cannot be recovered  it seems this would be a good sign that an irreversible problem has occurred and that I should simply close this socket connection  Is that a reasonable assumption     Yes it is   Once you ve received that exception  the socket won t ever work again   Closing it is is the only sensible thing to do      Is there ever a time when this IOException would occur while the socket connection is still being properly connected in the first place  rather than a working connection that failed at some point     No    Or at least  not without subverting proper behavior of the OS es network stack  the JVM and or your application         Is it wise to always call SocketChannel isConnected   before attempting a SocketChannel write         In general  it is a bad idea to call r isXYZ   before some call that uses the  external  resource r  There is a small chance that the state of the resource will change between the two calls   It is a better idea to do the action  catch the IOException  or whatever  resulting from the failed action and take whatever remedial action is required   In this particular case  calling isConnected   is pointless   The method is defined to return true if the socket was connected at some point in the past   It does not tell you if the connection is still live   The only way to determine if the connection is still alive is to attempt to use it  e g  do a read or write

User · Answer

Broken pipe means you wrote to a connection that is already closed by the other end   isConnected   does not detect this condition  Only a write does      is it wise to always call SocketChannel isConnected   before attempting a SocketChannel write     It is pointless  The socket itself is connected  You connected it  What may not be connected is the connection itself  and you can only determine that by trying it

User · Answer

Broken pipe simply means that the connection has failed   It is reasonable to assume that this is unrecoverable  and to then perform any required cleanup actions  closing connections  etc    I don t believe that you would ever see this simply due to the connection not yet being complete   If you are using non-blocking mode then the SocketChannel connect method will return false  and you will need to use the isConnectionPending and finishConnect methods to insure that the connection is complete   I would generally code based upon the expectation that things will work  and then catch exceptions to detect failure  rather than relying on frequent calls to  isConnected

[java] Java NIO: What does IOException: Broken pipe mean?

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