What happens to a named pipe if server crashes?

Question

Hi, i know little about pipes but have used one to connect two processes in my code in visual C++. The pipe is working well, but I need to add error handling to the same, hence wanted to know what will happen to a pipe if the server creating it crashed and how do I recognize it from client process?

Also what will happen if the client process tried accessing the same pipe, after the server crash, if no error handling is put in place?

Edit: What impact will be there on the memory if i keep creating new pipes (say by using system time as pipe name) while the previous was broken because of a server crash? Will these broken pipes be removed from the memory?

Answer 1

IIRC the ReadFile or WriteFile function will return FALSE and GetLastError() will return STATUS_PIPE_DISCONNECTED

I guess this kind of handling is implemented in your code, if not you should better add it ;-)

Answer 2

I just want to throw this out there.

If you want a survivable method for transferring data between two applications, you might consider using Mail Slots or even bringing in BizTalk or another message platform.

There are several things to consider:

1. what happens if the server is rebooted or loses power?
2. What happens if the server application becomes unresponsive?
3. What happens if the server application is killed or goes away completely?
4. What is the appropriate response of a client application in each of the above?

Each of those contexts represent a potential loss of data. If the data loss is unacceptable then named pipes is not the mechanism you should be using. Instead you need to persist the messages somehow.

Mail Slots, storing to a database, or even leveraging Biztalk can take care of the survivability of the message itself.

If 1 or 3 happens, then the named pipe goes away and must be recreated by a new instance of your server application. If #2 happens, then the pipe won't go away until someone either reboots the server or kills the server app and starts it again.

Regardless, the client application needs to handle the above issues. They boil down to connection failed problems. Depending on what the client does you might have it move into a wait state and let it ping the server every so often to see if it has come back again.

Without knowing the nature of the data and communication processes involved its hard to recommend a proper approach.