Man Page: rmr_wh_open





#include <rmr/rmr.h>

rmr_whid_t rmr_wh_open( void* vctx, char* target )


The rmr_wh_open function creates a direct link for sending, a wormhole, to another RMR based process. Sending messages through a wormhole requires that the connection be established overtly by the user application (via this function), and that the ID returned by rmr_wh_open be passed to the rmr_wh_send_msg function.

Vctx is the RMR void context pointer that was returned by the rmr_init function. Target is the name and port, or IP-address and port, combination for the process that the wormhole should be connected to. For example, “localhost:6123”.

When invoked, this function immediately attempts to connect to the target process. If the connection cannot be established, an error is returned to the caller, and no direct messages can be sent to the target. Once a wormhole is connected, the underlying transport mechanism (e.g. NNG) will provide reconnects should the connection be lost, however the handling of messages sent when a connection is broken is undetermined as each underlying transport mechanism may handle buffering and retries differently.


The rmr_wh_open function returns a type rmr_whid_t which must be passed to the rmr_wh_send_msg function when sending a message. The id may also be tested to determine success or failure of the connection by using the RMR_WH_CONNECTED macro and passing the ID as the parameter; a result of 1 indicates that the connection was established and that the ID is valid.


The following error values are specifically set by this RMR function. In some cases the error message of a system call is propagated up, and thus this list might be incomplete.


A parameter passed was not valid.


The user application does not have the ability to establish a wormhole to the indicated target (or maybe any target).


The connection was refused.


void*  rmc;
rmr_whid_t wh;

rmc = rmr_init( "43086", 4096, 0 ); // init context
wh = rmr_wh_open( rmc, "localhost:6123" );
if( !RMR_WH_CONNECTED( wh ) ) {
  fprintf( stderr, "unable to connect wormhole: %s\\n",
          strerror( errno ) );


rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3), rmr_wh_close(3), rmr_wh_send_msg(3), rmr_wh_state(3)