[OMPI users] MPI_Comm_accept()

[Adam Sylvester]

I'm using Open MPI 2.0.2 on RHEL 7.  I'm trying to use MPI_Open_port() /
MPI_Comm_accept() / MPI_Conn_connect().  My use case is that I'll have two
processes running on two machines that don't initially know about each
other (i.e. I can't do the typical mpirun with a list of IPs); eventually I
think I may need to use ompi-server to accomplish what I want but for now
I'm trying to test this out running two processes on the same machine with
some toy programs.

server.cpp creates the port, prints it, and waits for a client to accept
using it:

#include <mpi.h>
#include <iostream>

int main(int argc, char** argv)
{
    MPI_Init(NULL, NULL);

    char myport[MPI_MAX_PORT_NAME];
    MPI_Comm intercomm;

    MPI_Open_port(MPI_INFO_NULL, myport);
    std::cout << "Port name is " << myport << std::endl;

    MPI_Comm_accept(myport, MPI_INFO_NULL, 0, MPI_COMM_SELF, &intercomm);

    std::cout << "Accepted!" << std::endl;

    MPI_Finalize();
    return 0;
}

client.cpp takes in this port on the command line and tries to connect to
it:

#include <mpi.h>
#include <iostream>

int main(int argc, char** argv)
{
    MPI_Init(NULL, NULL);

    MPI_Comm intercomm;

    const std::string name(argv[1]);
    std::cout << "Trying with '" << name << "'" << std::endl;
    MPI_Comm_connect(name.c_str(), MPI_INFO_NULL, 0, MPI_COMM_SELF,
&intercomm);

    std::cout << "Connected!" << std::endl;

    MPI_Finalize();
    return 0;
}

I run the server first:
$ mpirun ./server
Port name is 2720137217.0:595361386

Then a second later I run the client:
$ mpirun ./client 2720137217.0:595361386
Trying with '2720137217.0:595361386'

Both programs hang for awhile and then eventually time out.  I have a
feeling I'm misunderstanding something and doing something dumb but from
all the examples I've seen online it seems like this should work.

Thanks for the help.
-Adam

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