MQTT client api and example

This code based on ESP8266 port of the embedded C client in Eclipse Paho project
(http://www.eclipse.org/paho/) and it port for espressif
ESP8266_RTOS_SDK by baoshi (https://github.com/baoshi/ESP-RTOS-Paho.git)

extras/paho_mqtt_c/MQTTESP8266.c

@@ -0,0 +1,187 @@
+/**
+  ******************************************************************************
+  * @file    MQTTESP8266.c
+  * @author  Baoshi <mail(at)ba0sh1(dot)com>
+  * @version 0.1
+  * @date    Sep 9, 2015
+  * @brief   Eclipse Paho ported to ESP8266 RTOS
+  *
+  ******************************************************************************
+  * @copyright
+  *
+  * Copyright (c) 2015, Baoshi Zhu. All rights reserved.
+  * Use of this source code is governed by a BSD-style license that can be
+  * found in the LICENSE.txt file.
+  *
+  * THIS SOFTWARE IS PROVIDED 'AS-IS', WITHOUT ANY EXPRESS OR IMPLIED
+  * WARRANTY.  IN NO EVENT WILL THE AUTHOR(S) BE HELD LIABLE FOR ANY DAMAGES
+  * ARISING FROM THE USE OF THIS SOFTWARE.
+  *
+  */
+
+#include <espressif/esp_common.h>
+#include <lwip/sockets.h>
+#include <lwip/inet.h>
+#include <lwip/netdb.h>
+#include <lwip/sys.h>
+#include <string.h>
+
+#include "MQTTESP8266.h"
+
+char  expired(Timer* timer)
+{
+    portTickType now = xTaskGetTickCount();
+    int32_t left = timer->end_time - now;
+    return (left < 0);
+}
+
+
+void  countdown_ms(Timer* timer, unsigned int timeout)
+{
+    portTickType now = xTaskGetTickCount();
+    timer->end_time = now + timeout / portTICK_RATE_MS;
+}
+
+
+void  countdown(Timer* timer, unsigned int timeout)
+{
+    countdown_ms(timer, timeout * 1000);
+}
+
+
+int  left_ms(Timer* timer)
+{
+    portTickType now = xTaskGetTickCount();
+    int32_t left = timer->end_time - now;
+    return (left < 0) ? 0 : left / portTICK_RATE_MS;
+}
+
+
+void  InitTimer(Timer* timer)
+{
+    timer->end_time = 0;
+}
+
+
+
+int  mqtt_esp_read(Network* n, unsigned char* buffer, int len, int timeout_ms)
+{
+    struct timeval tv;
+    fd_set fdset;
+    int rc = 0;
+    int rcvd = 0;
+    FD_ZERO(&fdset);
+    FD_SET(n->my_socket, &fdset);
+    // It seems tv_sec actually means FreeRTOS tick
+    tv.tv_sec = timeout_ms / portTICK_RATE_MS;
+    tv.tv_usec = 0;
+    rc = select(n->my_socket + 1, &fdset, 0, 0, &tv);
+    if ((rc > 0) && (FD_ISSET(n->my_socket, &fdset)))
+    {
+        rcvd = recv(n->my_socket, buffer, len, 0);
+    }
+    else
+    {
+        // select fail
+        return -1;
+    }
+    return rcvd;
+}
+
+
+int  mqtt_esp_write(Network* n, unsigned char* buffer, int len, int timeout_ms)
+{
+    struct timeval tv;
+    fd_set fdset;
+    int rc = 0;
+
+    FD_ZERO(&fdset);
+    FD_SET(n->my_socket, &fdset);
+    // It seems tv_sec actually means FreeRTOS tick
+    tv.tv_sec = timeout_ms / portTICK_RATE_MS;
+    tv.tv_usec = 0;
+    rc = select(n->my_socket + 1, 0, &fdset, 0, &tv);
+    if ((rc > 0) && (FD_ISSET(n->my_socket, &fdset)))
+    {
+        rc = send(n->my_socket, buffer, len, 0);
+    }
+    else
+    {
+        // select fail
+        return -1;
+    }
+    return rc;
+}
+
+
+
+void  NewNetwork(Network* n)
+{
+    n->my_socket = -1;
+    n->mqttread = mqtt_esp_read;
+    n->mqttwrite = mqtt_esp_write;
+}
+
+static int  host2addr(const char *hostname , struct in_addr *in)
+{
+    struct addrinfo hints, *servinfo, *p;
+    struct sockaddr_in *h;
+    int rv;
+
+    memset(&hints, 0, sizeof(hints));
+    hints.ai_family = AF_INET;
+    hints.ai_socktype = SOCK_STREAM;
+    rv = getaddrinfo(hostname, 0 , &hints , &servinfo);
+    if (rv != 0)
+    {
+        return rv;
+    }
+
+    // loop through all the results and get the first resolve
+    for (p = servinfo; p != 0; p = p->ai_next)
+    {
+        h = (struct sockaddr_in *)p->ai_addr;
+        in->s_addr = h->sin_addr.s_addr;
+    }
+    freeaddrinfo(servinfo); // all done with this structure
+    return 0;
+}
+
+
+int  ConnectNetwork(Network* n, const char* host, int port)
+{
+    struct sockaddr_in addr;
+    int ret;
+
+    if (host2addr(host, &(addr.sin_addr)) != 0)
+    {
+        return -1;
+    }
+
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(port);
+
+    n->my_socket = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
+    if( n->my_socket < 0 )
+    {
+        // error
+        return -1;
+    }
+    ret = connect(n->my_socket, ( struct sockaddr *)&addr, sizeof(struct sockaddr_in));
+    if( ret < 0 )
+    {
+        // error
+        close(n->my_socket);
+        return ret;
+    }
+
+    return ret;
+}
+
+
+int  DisconnectNetwork(Network* n)
+{
+    close(n->my_socket);
+    n->my_socket = -1;
+    return 0;
+}