Hi Hirak, In your scenario, the hanging on the client side is not a bug (but yes, it is not user-friendly). Here is the description about MPI_Comm_connect in the MPI 3.0 standard.

If the named port does not exist (or has been closed), MPI_COMM_CONNECT raises an error of class MPI_ERR_PORT.

run_good in your example.

If the port exists, but does not have a pending MPI_COMM_ACCEPT, the connection attempt will eventually time out after an implementation-defined time, or succeed when the server calls MPI_COMM_ACCEPT. In the case of a time out, MPI_COMM_CONNECT raises an error of class MPI_ERR_PORT.

MPI: A Message-Passing Interface Stand > This is the run_bad case, the "eventually time out" is implementation dependent : A Message-Passing Interface Standard . However, I just glanced over the code, it seems MPICH currently does not handle user-specified timeout through the info argument. I will look into code and keep you updated. Min On 5/11/16 11:39 PM, Roy, Hirak wrote:

Hi mpich team,

I am using MPICH 3.0.4 sock with dynamic connection (accept/connect).

I am facing issues with the following scenario, when there is a race condition in MPI_Comm_connect.

Here is the case

1>Server opens a port, writes the port info in a file, calls MPI_Comm_accept

2>Client1 & Client2 reads the port information from file and each client calls MPI_Comm_connect

3>Server accepts one client, disconnects, closes the port, exit

4>One of the client successfully connects, disconnects, exit

5>The other client hangs in MPI_Comm_connect

If you do the following steps, you can reproduce the issue

1>Please set compiler and installation path of MPICH in makefile

2>make : compiles

3>make run_bad

I have noticed that in case client calls MPI_Comm_connect after the port is closed, the connect calls successfully terminates with error (make run_good).

Please let me know whether it is a bug or not.

Please also let me know if the connect call can be configured with a timeout or not.

Thanks,

Hirak

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