---
name: "MPI_Comm_connect.openmpi"
section: "3"
platform: "linux"
package: "openmpi-doc"
version: "5.0.7-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/MPI_Comm_connect.openmpi"
---

# MPI\_Comm\_connect.openmpi(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*. The *MPI\_Comm\_connect* call must only be called after the *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* 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\_thread*, after *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* 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\_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* was called on that communicator. If called on a window or file, acts as if *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* then *MPI\_Comm\_set\_errhandler*

- •

  *MPI\_File\_create\_errhandler* then *MPI\_File\_set\_errhandler*

- •

  *MPI\_Session\_create\_errhandler* then *MPI\_Session\_set\_errhandler* or at *MPI\_Session\_init*

- •

  *MPI\_Win\_create\_errhandler* then *MPI\_Win\_set\_errhandler*

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

See the *MPI man page* for a full list of *MPI error codes*.

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

**SEE ALSO:**

- •

  *MPI\_Comm\_accept*

## COPYRIGHT

2003-2025, The Open MPI Community