paho.mqtt.embedded-c MQTTPacket transport.c hacking

/*******************************************************************************
 *          paho.mqtt.embedded-c MQTTPacket transport.c hacking
 * 说明：
 *     跟一下paho.mqtt.embedded-c中的MQTT协议transport.c怎么使用。
 * 
 *                                          2017-12-6 深圳 南山平山村 曾剑锋
 ******************************************************************************/


/*******************************************************************************
 * Copyright (c) 2014 IBM Corp.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 *   http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *    Ian Craggs - initial API and implementation and/or initial documentation
 *    Sergio R. Caprile - "commonalization" from prior samples and/or documentation extension
 *******************************************************************************/

#include <sys/types.h>

#if !defined(SOCKET_ERROR)
    /** error in socket operation */
    #define SOCKET_ERROR -1
#endif

#if defined(WIN32)
/* default on Windows is 64 - increase to make Linux and Windows the same */
#define FD_SETSIZE 1024
#include <winsock2.h>
#include <ws2tcpip.h>
#define MAXHOSTNAMELEN 256
#define EAGAIN WSAEWOULDBLOCK
#define EINTR WSAEINTR
#define EINVAL WSAEINVAL
#define EINPROGRESS WSAEINPROGRESS
#define EWOULDBLOCK WSAEWOULDBLOCK
#define ENOTCONN WSAENOTCONN
#define ECONNRESET WSAECONNRESET
#define ioctl ioctlsocket
#define socklen_t int
#else
#define INVALID_SOCKET SOCKET_ERROR
#include <sys/socket.h>
#include <sys/param.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#endif

#if defined(WIN32)
#include <Iphlpapi.h>
#else
#include <sys/ioctl.h>
#include <net/if.h>
#endif

/**
This simple low-level implementation assumes a single connection for a single thread. Thus, a static
variable is used for that connection.
On other scenarios, the user must solve this by taking into account that the current implementation of
MQTTPacket_read() has a function pointer for a function call to get the data to a buffer, but no provisions
to know the caller or other indicator (the socket id): int (*getfn)(unsigned char*, int)
*/
static int mysock = INVALID_SOCKET;


int transport_sendPacketBuffer(int sock, unsigned char* buf, int buflen)
{
    int rc = 0;
    // 写入socket，buf为字节buffer， buflen为需要写入的字节长度
    // rc为最终写入的字节长度
    rc = write(sock, buf, buflen);
    return rc;
}


int transport_getdata(unsigned char* buf, int count)
{
    // 读取socket，buf为字节buffer， count为需要读取的字节长度
    // rc为最终读取的字节长度
    int rc = recv(mysock, buf, count, 0);
    //printf("received %d bytes count %d
", rc, (int)count);
    return rc;
}

int transport_getdatanb(void *sck, unsigned char* buf, int count)
{
    int sock = *((int *)sck);     /* sck: pointer to whatever the system may use to identify the transport */
    /* this call will return after the timeout set on initialization if no bytes;
       in your system you will use whatever you use to get whichever outstanding
       bytes your socket equivalent has ready to be extracted right now, if any,
       or return immediately */
    int rc = recv(sock, buf, count, 0);    
    if (rc == -1) {
        /* check error conditions from your system here, and return -1 */
        return 0;
    }
    return rc;
}

/**
return >=0 for a socket descriptor, <0 for an error code
@todo Basically moved from the sample without changes, should accomodate same usage for 'sock' for clarity,
removing indirections
*/
// 兼容各种平台下依照addr、port打开socket的方法
int transport_open(char* addr, int port)
{
    // 获取mysock指针
    int* sock = &mysock;
    // 传输方式为socket流
    int type = SOCK_STREAM;
    struct sockaddr_in address;
#if defined(AF_INET6)
    struct sockaddr_in6 address6;
#endif
    int rc = -1;
#if defined(WIN32)
    short family;
#else
    sa_family_t family = AF_INET;
#endif
    struct addrinfo *result = NULL;
    struct addrinfo hints = {0, AF_UNSPEC, SOCK_STREAM, IPPROTO_TCP, 0, NULL, NULL, NULL};
    static struct timeval tv;

    *sock = -1;
    if (addr[0] == '[')
      ++addr;

    if ((rc = getaddrinfo(addr, NULL, &hints, &result)) == 0)
    {
        struct addrinfo* res = result;

        /* prefer ip4 addresses */
        while (res)
        {
            if (res->ai_family == AF_INET)
            {
                result = res;
                break;
            }
            res = res->ai_next;
        }

#if defined(AF_INET6)
        if (result->ai_family == AF_INET6)
        {
            address6.sin6_port = htons(port);
            address6.sin6_family = family = AF_INET6;
            address6.sin6_addr = ((struct sockaddr_in6*)(result->ai_addr))->sin6_addr;
        }
        else
#endif
        if (result->ai_family == AF_INET)
        {
            address.sin_port = htons(port);
            address.sin_family = family = AF_INET;
            address.sin_addr = ((struct sockaddr_in*)(result->ai_addr))->sin_addr;
        }
        else
            rc = -1;

        freeaddrinfo(result);
    }

    if (rc == 0)
    {
        *sock =    socket(family, type, 0);
        if (*sock != -1)
        {
#if defined(NOSIGPIPE)
            int opt = 1;

            if (setsockopt(*sock, SOL_SOCKET, SO_NOSIGPIPE, (void*)&opt, sizeof(opt)) != 0)
                Log(TRACE_MIN, -1, "Could not set SO_NOSIGPIPE for socket %d", *sock);
#endif

            if (family == AF_INET)
                rc = connect(*sock, (struct sockaddr*)&address, sizeof(address));
    #if defined(AF_INET6)
            else
                rc = connect(*sock, (struct sockaddr*)&address6, sizeof(address6));
    #endif
        }
    }
    if (mysock == INVALID_SOCKET)
        return rc;

    tv.tv_sec = 1;  /* 1 second Timeout */
    tv.tv_usec = 0;  
    setsockopt(mysock, SOL_SOCKET, SO_RCVTIMEO, (char *)&tv,sizeof(struct timeval));
    return mysock;
}

// 主要就是关闭socket了
int transport_close(int sock)
{
int rc;

    rc = shutdown(sock, SHUT_WR);
    rc = recv(sock, NULL, (size_t)0, 0);
    rc = close(sock);

    return rc;
}