How to encapsulate library handle in Perl XS

I wanted to send/receive MQTT messages from Perl. For various reasons (MQTT 5 support, TLS) I don't want to use existing Perl libraries. So I tried to create XS bindings to Paho MQTT C Library. I somehow adapted provided example to link Perl module to Paho library using relly basic Perl XS:

#define PERL_NO_GET_CONTEXT
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

#include "ppport.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <MQTTClient.h>
#define CLIENTID    "ExampleClientPub"
#define QOS         1
#define TIMEOUT     10000L

MODULE = paho              PACKAGE = paho         

int
mqtt_connect_and_send (server_address, username, topic, payload)
    char * server_address
    char * username
    char * topic
    char * payload
CODE:
    MQTTClient client;
    MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
    MQTTClient_message msg = MQTTClient_message_initializer;
    MQTTClient_deliveryToken token;
    int rc;

    /* connect to server */
    MQTTClient_create(&client, server_address, CLIENTID,
        MQTTCLIENT_PERSISTENCE_NONE, NULL);
    conn_opts.keepAliveInterval = 20;
    conn_opts.cleansession = 1;
    conn_opts.username = username;

    if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
    {
        /* didn't connect */
        die("Failed to connect, return code %d", rc);
    }

    /* fill in message data and send it */
    msg.payload = payload;
    msg.payloadlen = strlen(payload);
    msg.qos = QOS;
    msg.retained = 0;
    MQTTClient_publishMessage(client, topic, &msg, &token);
    rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);

    /* shutdown connection */
    MQTTClient_disconnect(client, 10000);
    MQTTClient_destroy(&client);

    if (rc != MQTTCLIENT_SUCCESS) {
        /* didn't send the message */
        die("Failed to send message, return code %d", rc);
    }

    RETVAL = 1;
OUTPUT:
    RETVAL

This is working OK. But now I want to split function mqtt_connect_and_send to 3 functions: mqtt_connect, mqtt_send_message, mqtt_disconnect. And my question is - how to do this? How to create a handle (client in my case) in XS in one function, return it to Perl to somehow store it in a scalar and use that handle in ahother XS function to be used to send more messages? I want to be able to do this in Perl:

my $client = paho::mqtt_connect($server_spec, $username, $password, $more_opts);
$success = paho::mqtt_send($client, $data, $message_opts);
# ... more of mqtt_send's
paho::mqtt_disconnect($server)

I tried to set RETVAL RETVAL = &client or mXPUSHu(&client) but that I didn't get anywhere with that. Can you point me to some example how to get client to Perl and then back to XS to be used again?

Thank you.

Here is an example of how you can return the client as a perl object:

#define PERL_NO_GET_CONTEXT
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"
#include "ppport.h"       // allow the module to be built using older versions of Perl

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <MQTTClient.h>
#define CLIENTID    "ExampleClientPub"
#define QOS         1
#define TIMEOUT     10000L

UV get_hash_uv(HV *hash, const char *key) {
#define get_hash_uv(a,b) get_hash_uv(aTHX_ a,b)
    SV * key_sv = newSVpv (key, strlen (key));
    UV value;
    if (hv_exists_ent (hash, key_sv, 0)) {
        HE *he = hv_fetch_ent (hash, key_sv, 0, 0);
        SV *val = HeVAL (he);
        STRLEN val_length;
        char * val_pv = SvPV (val, val_length);
        if (SvIOK (val)) {
            value = SvUV (val);
        }
        else {
            croak("Value of hash key '%s' is not a number", key);
        }
    }
    else {
        croak("The hash key for '%s' doesn't exist", key);
    }
    return value;
}


MODULE = Paho   PACKAGE = Paho
PROTOTYPES: DISABLE

SV *
mqtt_connect(server_address, username)
    char *server_address
    char *username
  CODE:
    int rc;
    MQTTClient client;  // void *
    MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;

    MQTTClient_create(&client, server_address, CLIENTID,
        MQTTCLIENT_PERSISTENCE_NONE, NULL);
    conn_opts.keepAliveInterval = 20;
    conn_opts.cleansession = 1;
    conn_opts.username = username;

    if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
    {
        MQTTClient_destroy(&client);
        croak("Failed to connect, return code %d", rc);
    }
    HV *hash = newHV();
    SV *self = newRV_noinc( (SV *)hash );
    SV *sv = newSVuv(PTR2IV(client));
    hv_store (hash, "client", strlen ("client"), sv, 0);
    RETVAL = sv_bless(self, gv_stashpv( "Paho::Client", GV_ADD ) );

  OUTPUT:
    RETVAL

MODULE = Paho  PACKAGE = Paho::Client

void
DESTROY(self)
       SV *self
   CODE:
       MQTTClient client;  // void *

       HV *hv = (HV *) SvRV(self);
       UV addr = get_hash_uv(hv, "client");
       client = (MQTTClient ) INT2PTR(SV*, addr);

       MQTTClient_destroy(&client);
       printf("Paho::Client destroy\n");

I am not able to test this yet, because I do not have good values for the input parameters server_address and username. Please provide data that we can test with.