(转）linux下和云端通讯的例程, ubuntu和openwrt下实验成功(二)

前言: 上节用纯linux的函数实现了和云端通讯, 本节开始利用传说中的神器libcurl

话说一个网络程序员对书法十分感兴趣，退休后决定在这方面有所建树。 于是花重金购买了上等的文房四宝。    
一日，饭后突生雅兴，一番磨墨拟纸，  并点上了上好的檀香，颇有王羲之风范，  又具颜真卿气势，定神片刻，泼墨挥毫，    
郑重地写下一行字：libcurl.

由此可知libcurl的刻骨铭心!
官方文档请参考这里 http://curl.haxx.se/libcurl/c/curl_easy_setopt.html

刚接触 libcurl的时候, 自然的想到按照常规的思路来连接云端: 先连接Web, 再发送请求, 然后等待接受返回数据. 
这样思路的代码如下

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/*----------------------------------------------------------------------------------------------------
名称: http_cloud_curl_simple.c
功能: 利用libcurl的API顺序实现云端通讯, 未利用回调机制
-----------------------------------------------------------------------------------------------------*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>
#include <assert.h>

#include "../http_cloud.h"

#define DBG printf

//-----------------------------------------------------------------------------------------
static void get_local_time(char *pc_str)
{
    time_t now;
    struct tm *timenow;

    assert(pc_str != NULL);

    time(&now);
    timenow = localtime(&now);
    sprintf(pc_str, "%04d-%02d-%02dT%02d:%02d:%02d", timenow->tm_year+1900, timenow->tm_mon+1, timenow->tm_mday,
                    timenow->tm_hour, timenow->tm_min, timenow->tm_sec);
}

/* Auxiliary function that waits on the socket. */
static int wait_on_socket(curl_socket_t sockfd, int for_recv, long timeout_ms)
{
  struct timeval tv;
  fd_set infd, outfd, errfd;
  int res;

  tv.tv_sec = timeout_ms / 1000;
  tv.tv_usec= (timeout_ms % 1000) * 1000;

  FD_ZERO(&infd);
  FD_ZERO(&outfd);
  FD_ZERO(&errfd);

  FD_SET(sockfd, &errfd); /* always check for error */

  if(for_recv) {
    FD_SET(sockfd, &infd);
  }
  else {
    FD_SET(sockfd, &outfd);
  }

  /* select() returns the number of signalled sockets or -1 */
  res = select(sockfd + 1, &infd, &outfd, &errfd, &tv);
  return res;
}

static char connect_cloud(char *pc_ret, const char *host_addr, const int portno, const char *request)
{
    CURL *curl;
  CURLcode res;
  /* Minimalistic http request */
  //const char *request = "GET / HTTP/1.0
Host: example.com

";
  //char request[1024] = "";
  curl_socket_t sockfd; /* socket */
  long sockextr;
  size_t iolen;
  curl_off_t nread;
  int iLen = 0;
  char cRet = 0;

  assert((pc_ret != NULL) && (host_addr != NULL) && (request != NULL));

  //curl_global_init(CURL_GLOBAL_DEFAULT);
  curl = curl_easy_init();
  if (!curl)    return 0;

  //curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
  curl_easy_setopt(curl, CURLOPT_URL, host_addr);
  /* Do not do the transfer - only connect to host */
  curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
  res = curl_easy_perform(curl);
  if(CURLE_OK != res) {
    printf("Error: %s
", strerror(res));
    return -1;
  }

  /* Extract the socket from the curl handle - we'll need it for waiting.
   * Note that this API takes a pointer to a 'long' while we use
   * curl_socket_t for sockets otherwise.
   */
  res = curl_easy_getinfo(curl, CURLINFO_LASTSOCKET, &sockextr);
  if(CURLE_OK != res) {
    printf("Error: %s
", curl_easy_strerror(res));
    return -2;
  }

  sockfd = sockextr;
  /* wait for the socket to become ready for sending */
  if(!wait_on_socket(sockfd, 0, 60000L)) {
    printf("Error: timeout.
");
    return -3;
  }

  /* Send the request. Real applications should check the iolen
   * to see if all the request has been sent */
  res = curl_easy_send(curl, request, strlen(request), &iolen);
  if(CURLE_OK != res) {
    printf("Error: %s
", curl_easy_strerror(res));
    return -4;
  }

  /* read the response */
  char buf[1024];
  while(1) {
    wait_on_socket(sockfd, 1, 60000L);
    res = curl_easy_recv(curl, buf, 1024, &iolen);

    if(CURLE_OK != res)
      break;

    nread = (curl_off_t)iolen;
  }
  buf[nread] = '';
  DBG("Received (%" CURL_FORMAT_CURL_OFF_T "), %s
", nread, buf);

  /* always cleanup */
  curl_easy_cleanup(curl);

  pc_ret = strstr(buf, "

");
    if (pc_ret) {
        pc_ret += 4;
        DBG("ret = %s
", pc_ret);
    }

  return 1;
}

#if (YEELINK == 1)
int yeelink_create_data(const int device_id, const int sensor_id, const float device_value)
{
    char pc_ret[200], request[1024], pc_json[100], pc_time[30], pc_host_file[100], pc_header[100], ret;
    int len;

    sprintf(pc_host_file, "v1.0/device/%d/sensor/%d/datapoints", device_id, sensor_id);
    sprintf(pc_header, "U-ApiKey: %s", YEELINK_API_KEY);

    get_local_time(pc_time);
    sprintf(pc_json, "{"timestamp":"%s","value":%.2f}", pc_time, device_value);
    len = strlen(pc_json);

    sprintf(request, "POST /%s HTTP/1.1
Host: %s
Accept: */*
%s
Content-Length: %d
Content-Type: application/x-www-form-urlencoded
Connection: Close

%s
",
        pc_host_file, YEELINK_HOST, pc_header, len, pc_json);
    DBG("request = %s
", request);

    ret = connect_cloud(pc_ret, YEELINK_HOST, YEELINK_PORT, request);

    return(ret);
}
#endif

#if (LEWEI50 == 1)
//curl --request POST http://www.lewei50.com/api/V1/Gateway/UpdateSensors/01 --data "[{"Name":"T1","Value":"23.08"}]" --header "userkey:36be8ff22f794f1e8a0bee3336eef237"
int lewei50_create_data(const char *device_id, const float device_value)
{
    char pc_ret[200], request[1024], pc_json[100], pc_header[100], ret;
    int len;

    assert(device_id != NULL);

    sprintf(pc_header, "userkey: %s", LEWEI50_USER_KEY);
    sprintf(pc_json, "[{"Name":"%s","Value":"%.2f"}]", device_id, device_value);
    len = strlen(pc_json);

    sprintf(request, "POST /%s HTTP/1.1
Host: %s
Accept: */*
%s
Content-Length: %d
Content-Type: application/x-www-form-urlencoded
Connection: Close

%s
",
        LEWEI50_HOST_FILE, LEWEI50_HOST, pc_header, len, pc_json);
    DBG("request = %s
", request);

    ret = connect_cloud(pc_ret, LEWEI50_HOST, LEWEI50_PORT, request);

    return(ret);
}
#endif

//-------------------------------------------------------------------
int main(void)
{
    float f_value = 15.02;
    int i_tmp;

    time_t t;
  srand((unsigned)time(&t));    //初始化随机种子, 否则随机数不随机

    i_tmp = rand();
    i_tmp -= (i_tmp >> 4 << 4);
  f_value += i_tmp;

#if (YEELINK == 1)
    yeelink_create_data(YEELINK_DEVICE_ID, YEELINK_SENSOR_ID, f_value);
#endif

#if (LEWEI50 == 1)
    lewei50_create_data(LEWEI50_DEVICE_ID, f_value);
#endif

    return 1;
}

Makefile: 注意openwrt的连接参数要多加的, 为了这几个字母, 折腾了好长时间

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OPENWRT = 1

ifeq ($(OPENWRT), 1)
    CC = ~/OpenWrt-SDK-ar71xx-for-linux-i486-gcc-4.6-linaro_uClibc-0.9.33.2/staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/bin/mips-openwrt-linux-gcc
    CFLAGS += -I ~/openwrt-lib/include -L ~/openwrt-lib/lib
    LFLAGS += -lcurl -lcrypto -lz -lssl

else
    CC = gcc
    LFLAGS += -lcurl
endif

CFLAGS += -Wall -O2
#CFLAGS += -g

#可执行文件名和相关的obj文件
APP_BINARY = http_cloud
SRCS += http_cloud_curl_simple.c
OBJS = $(SRCS:.c=.o)

all: APP_FILE

APP_FILE: $(OBJS)
    $(CC) $(CFLAGS) $(OBJS) -o $(APP_BINARY) $(LFLAGS)

.PHONY: clean
clean:
    @echo "cleanning project"
    $(RM) *.a $(OBJS) *~ *.so *.lo $(APP_BINARY)
    @echo "clean completed"

openwrt下的运行结果如下
root@OpenWrt:/xutest# ./http_cloud_libcurl
yeelini ret = HTTP/1.1 200 OK
Server: nginx/1.1.19
Date: Thu, 07 Nov 2013 00:56:56 GMT
Content-Type: text/html
Transfer-Encoding: chunked
Connection: close
X-Powered-By: PHP/5.3.10-1ubuntu3.6
Set-Cookie: CAKEPHP=dfvacsdpb8ls802dulnt695kk2; expires=Fri, 15-Nov-2013 08:56:56 GMT; path=/
P3P: CP="NOI ADM DEV PSAi COM NAV OUR OTRo STP IND DEM"

lewei50 ret = HTTP/1.1 200 OK
Date: Thu, 07 Nov 2013 00:56:56 GMT
Content-Type: application/json; charset=utf-8
Content-Length: 44
Connection: close
Cache-Control: private
Set-Cookie: SERVERID=a4a5b2bbca16d8c8b2ba6d5b6e55f36e|1383785816|1383785816;Path=/

{"Successful":true,"Message":"Successful. "}

root@OpenWrt:/xutest# 

---

这仅仅是libcurl最最简单的应用, 本着'师夷长技以制夷'的原则, 继续看官方文档中......