MPI_COMM_CONNECT(3)				     Open MPI				       MPI_COMM_CONNECT(3)

MPI_Comm_connect — Establishes communication with a server.

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Comm_connect(const char *port_name, MPI_Info info, int root,
	      MPI_Comm comm, MPI_Comm *newcomm)

   Fortran Syntax
	  USE MPI
	  ! or the older form: INCLUDE 'mpif.h'

	  MPI_COMM_CONNECT(PORT_NAME, INFO, ROOT, COMM, NEWCOMM, IERROR)
	      CHARACTER*(*)   PORT_NAME
	      INTEGER	  INFO, ROOT, COMM, NEWCOMM, IERROR

   Fortran 2008 Syntax
	  USE mpi_f08

	  MPI_Comm_connect(port_name, info, root, comm, newcomm, ierror)
	      CHARACTER(LEN=*), INTENT(IN) :: port_name
	      TYPE(MPI_Info), INTENT(IN) :: info
	      INTEGER, INTENT(IN) :: root
	      TYPE(MPI_Comm), INTENT(IN) :: comm
	      TYPE(MPI_Comm), INTENT(OUT) :: newcomm
	      INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS
       • port_name : Port name (string, used only on root).

       •

	 info (Options given by root for the connect (handle, used only on)
		root). No options currently supported.

       • root : Rank in comm of root node (integer).

       • comm : Intracommunicator over which call is collective (handle).

OUTPUT PARAMETERS
       • newcomm : Intercommunicator with client as remote group (handle)

       • ierror : Fortran only: Error status (integer).

DESCRIPTION
       MPI_Comm_connect	 establishes communication with a server specified by port_name. It is collective over the
       calling communicator and returns an  intercommunicator  in  which  the  remote  group  participated  in	an
       MPI_Comm_accept <#mpi-comm-accept>. The MPI_Comm_connect call must only be called after the MPI_Comm_accept
       <#mpi-comm-accept>  call	 has  been  made  by the MPI job acting as the server.	If the named port does not
       exist (or has been closed), MPI_Comm_connect raises  an	error  of  class  MPI_ERR_PORT.	 MPI  provides	no
       guarantee  of  fairness	in servicing connection attempts. That is, connection attempts are not necessarily
       satisfied in the order in which they were initiated, and competition from  other	 connection  attempts  may
       prevent a particular connection attempt from being satisfied. The port_name parameter is the address of the
       server. It must be the same as the name returned by MPI_Open_port <#mpi-open-port> on the server.

ERRORS
       Almost  all MPI routines return an error value; C routines as the return result of the function and Fortran
       routines in the last argument.

       Before the error value is returned, the current MPI error handler associated with the communication  object
       (e.g.,  communicator, window, file) is called.  If no communication object is associated with the MPI call,
       then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler.  When
       MPI_COMM_SELF  is  not  initialized  (i.e., before MPI_Init <#mpi-init>/MPI_Init_thread <#mpi-init-thread>,
       after MPI_Finalize <#mpi-finalize>, or when using the Sessions Model  exclusively)  the	error  raises  the
       initial	error  handler.	 The  initial  error  handler can be changed by calling MPI_Comm_set_errhandler <#
       mpi-comm-set-errhandler> on MPI_COMM_SELF when using the World model,  or  the  mpi_initial_errhandler  CLI
       argument	  to   mpiexec	 or   info  key	 to  MPI_Comm_spawn  <#mpi-comm-spawn>/MPI_Comm_spawn_multiple	<#
       mpi-comm-spawn-multiple>.  If no other appropriate error handler has been set, then  the	 MPI_ERRORS_RETURN
       error  handler  is  called  for	MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all
       other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or  session.  When
	 called on a communicator, it acts as if MPI_Abort <#mpi-abort> was called on that communicator. If called
	 on  a window or file, acts as if MPI_Abort <#mpi-abort> was called on a communicator containing the group
	 of processes in the corresponding window or file. If called on a session, aborts only the local process.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler	<#mpi-comm-create-errhandler>	  then	   MPI_Comm_set_errhandler	<#
	 mpi-comm-set-errhandler>

       • MPI_File_create_errhandler	 <#mpi-file-create-errhandler>	   then	    MPI_File_set_errhandler	<#
	 mpi-file-set-errhandler>

       • MPI_Session_create_errhandler	 <#mpi-session-create-errhandler>   then   MPI_Session_set_errhandler	<#
	 mpi-session-set-errhandler> or at MPI_Session_init <#mpi-session-init>

       • MPI_Win_create_errhandler	<#mpi-win-create-errhandler>	  then	    MPI_Win_set_errhandler	<#
	 mpi-win-set-errhandler>

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>.

       See the Error Handling section of the MPI-3.1 standard for more information.

       See also:

	  • MPI_Comm_accept <#mpi-comm-accept>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026				       MPI_COMM_CONNECT(3)
