Comment 2 for bug 1261683

The documentation says:

 * Important note
 *
 * The following functions that deal with network operations will return
 * MOSQ_ERR_SUCCESS on success, but this does not mean that the operation has
 * taken place. An attempt will be made to write the network data, but if the
 * socket is not available for writing at that time then the packet will not be
 * sent. To ensure the packet is sent, call mosquitto_loop() (which must also
 * be called to process incoming network data).
 * This is especially important when disconnecting a client that has a will. If
 * the broker does not receive the DISCONNECT command, it will assume that the
 * client has disconnected unexpectedly and send the will.
 *
 * mosquitto_connect()
 * mosquitto_disconnect()
 * mosquitto_subscribe()
 * mosquitto_unsubscribe()
 * mosquitto_publish()

You haven't called one of the mosquitto_loop*() functions, so you will
never receive a CONNACK. You've also not called mosquitto_lib_init().

If you want the publish to happen after a successful connection, put
it in the on_connect() callback. If you want to disconnect after a
successful publish, but that in the on_publish() callback and use a
while loop to call mosquitto_loop() (or just use
mosquitto_loop_forever()).

On Tue, Dec 17, 2013 at 11:05 AM, Yun Wu <wuyun1984_1984@163.com> wrote:
> ** Description changed:
>
> It seems that blocking mode is not really supported.
>
> Topology: publisher -- broker -- subscriber
> Publisher simply publish a message then exit.
> Subscriber sometimes can receive message published by publisher, but sometimes not.
>
> The root cause is, libmosquitto does not really support blocking mode.
> mosquitto_connect_bind --> _mosquitto_reconnect --> _mosquitto_send_connect
> That means mosquitto_connect_bind() does not wait until CONNACK arrives.
>
> Logs can prove that:
> ----
> 1387273535: New connection from 172.18.111.243 on port 1883.
> 1387273535: New client connected from 172.18.111.243 as TestClientId (c1, k3600).
> 1387273535: Sending CONNACK to TestClientId (0)
> 1387273535: Socket error on client TestClientId, disconnecting.
> ----
> We can see:
> 1) Broker has not received PUBLISH message from publisher.
> 2) Broker has not received DISCONNECT message from publisher.
>
> All because blocking mode is not really supported.
>
> - In blocking mode,
> + In blocking mode,
> mosquitto_connect_bind should wait until CONNACK arrives;
> If QoS not 0, mosquitto_publish should wait unit ...
> mosquitto_subscribe should wait unit ...
> ...
> +
> +
> +
> + Here is code of the publisher:
> +
> + #include <errno.h>
> + #include <stdio.h>
> + #include <stdlib.h>
> + #include <string.h>
> + #include <unistd.h>
> + #include "mosquitto.h"
> +
> + #define dbg(fmt, args...) \
> + printf("%s(%u): "fmt"\n", __FUNCTION__, __LINE__, ##args)
> +
> + int main(int argc, char *argv[])
> + {
> + struct mosquitto *mosq = NULL;
> + int rv;
> + const char topic[] = "TestTopic";
> + const char buf[] = "Hello, world";
> +
> + if (MOSQ_ERR_SUCCESS != mosquitto_lib_init()) {
> + return -1;
> + }
> +
> + if (NULL == (mosq = mosquitto_new("TestClientId", 1, NULL))) {
> + dbg("mosquitto_new() failed");
> + rv = -1;
> + goto quit;
> + }
> +
> + rv = mosquitto_connect_bind(mosq, "172.18.111.245", 1883, 3600, "172.18.111.243");
> + if (MOSQ_ERR_SUCCESS != rv) {
> + dbg("mosquitto_connect_bind() failed: %s", mosquitto_strerror(rv));
> + if (MOSQ_ERR_ERRNO == rv) {
> + dbg("errno = %d: %s", errno, strerror(errno));
> + }
> + rv = -1;
> + goto quit;
> + }
> +
> + if (MOSQ_ERR_SUCCESS != mosquitto_publish(mosq, NULL, topic, sizeof(buf), buf, 0, 0)) {
> + dbg("mosquitto_publish to %s failed", topic);
> + rv = -1;
> + goto quit;
> + }
> +
> + quit:
> + if (NULL != mosq) {
> + mosquitto_disconnect(mosq);
> + mosquitto_destroy(mosq);
> + }
> + mosquitto_lib_cleanup();
> + return rv;
> + }
>
> --
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> https://bugs.launchpad.net/bugs/1261683
>
> Title:
> Blocking mode is not really supported
>
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