Paho MQTT C客戶端是一個使用標準C編寫的流暢的MQTT。 實際上包含了兩個C API，同步的和異步的，分別爲MQTTClient和MQTTAsync。同步的API可以更簡單更使用，執行完操作後，一些調用會被阻攔，編程也更容易；而在異步API沒有調用的阻攔操作，所有API的調用都是通過會調來實現的，這使得API更適合有窗口環境的操作系統，許多應用沒有主線程控制。
linux環境：
在linux環境下建立MQTT C 客戶端：
git clone https://github.com/eclipse/paho.mqtt.c.git
cd org.eclipse.paho.mqtt.c.git
make
安裝MQTT
sudo make install
在windows環境下
在Windows下使用Visual Studio 或者Visual C++創建
git clone https://github.com/eclipse/paho.mqtt.c.git
cd org.eclipse.paho.mqtt.c.git
msbuild "Windows Build\Paho C MQTT APIs.sln" /p:Configuration=Release
爲了設置msbuild的路徑，可以運行 vcvars32.bat，它的創建如下：
C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\bin
以下是一個簡單的同步類型的MQTT C客戶端：
#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "MQTTClient.h"
#define ADDRESS "tcp://localhost:1883"
#define CLIENTID "ExampleClientPub"
#define TOPIC "MQTT Examples"
#define PAYLOAD "Hello World!"
#define QOS 1
#define TIMEOUT 10000L
int main(int argc, char* argv[])
{
MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
MQTTClient_message pubmsg = MQTTClient_message_initializer;
MQTTClient_deliveryToken token;
int rc;
MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_NONE, NULL);
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
exit(-1);
}
pubmsg.payload = PAYLOAD;
pubmsg.payloadlen = strlen(PAYLOAD);
pubmsg.qos = QOS;
pubmsg.retained = 0;
MQTTClient_publishMessage(client, TOPIC, &pubmsg, &token);
printf("Waiting for up to %d seconds for publication of %s\n"
"on topic %s for client with ClientID: %s\n",
(int)(TIMEOUT/1000), PAYLOAD, TOPIC, CLIENTID);
rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);
printf("Message with delivery token %d delivered\n", token);
MQTTClient_disconnect(client, 10000);
MQTTClient_destroy(&client);
return rc;
}