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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1. /*----------------------------------------------------------------------------------------------------
   
2. 名称: http_cloud_curl_simple.c
   
3. 功能: 利用libcurl的API顺序实现云端通讯, 未利用回调机制
   
4. -----------------------------------------------------------------------------------------------------*/
   
5. #include <stdio.h>
   
6. #include <stdlib.h>
   
7. #include <string.h>
   
8. #include <curl/curl.h>
   
9. #include <assert.h>
   
10. 
    
11. #include "../http_cloud.h"
    
12. 
    
13. #define DBG printf
    
14. 
    
15. //-----------------------------------------------------------------------------------------
    
16. static void get_local_time(char *pc_str)
    
17. {
    
18.     time_t now;
    
19.     struct tm *timenow;
    
20. 
    
21.     assert(pc_str != NULL);
    
22. 
    
23.     time(&now);
    
24.     timenow = localtime(&now);
    
25.     sprintf(pc_str, "%04d-%02d-%02dT%02d:%02d:%02d", timenow->tm_year+1900, timenow->tm_mon+1, timenow->tm_mday,
    
26.                     timenow->tm_hour, timenow->tm_min, timenow->tm_sec);
    
27. }
    
28. 
    
29. /* Auxiliary function that waits on the socket. */
    
30. static int wait_on_socket(curl_socket_t sockfd, int for_recv, long timeout_ms)
    
31. {
    
32.   struct timeval tv;
    
33.   fd_set infd, outfd, errfd;
    
34.   int res;
    
35. 
    
36.   tv.tv_sec = timeout_ms / 1000;
    
37.   tv.tv_usec= (timeout_ms % 1000) * 1000;
    
38. 
    
39.   FD_ZERO(&infd);
    
40.   FD_ZERO(&outfd);
    
41.   FD_ZERO(&errfd);
    
42. 
    
43.   FD_SET(sockfd, &errfd); /* always check for error */
    
44. 
    
45.   if(for_recv) {
    
46.     FD_SET(sockfd, &infd);
    
47.   }
    
48.   else {
    
49.     FD_SET(sockfd, &outfd);
    
50.   }
    
51. 
    
52.   /* select() returns the number of signalled sockets or -1 */
    
53.   res = select(sockfd + 1, &infd, &outfd, &errfd, &tv);
    
54.   return res;
    
55. }
    
56. 
    
57. static char connect_cloud(char *pc_ret, const char *host_addr, const int portno, const char *request)
    
58. {
    
59.     CURL *curl;
    
60.   CURLcode res;
    
61.   /* Minimalistic http request */
    
62.   //const char *request = "GET / HTTP/1.0\r\nHost: example.com\r\n\r\n";
    
63.   //char request[1024] = "";
    
64.   curl_socket_t sockfd; /* socket */
    
65.   long sockextr;
    
66.   size_t iolen;
    
67.   curl_off_t nread;
    
68.   int iLen = 0;
    
69.   char cRet = 0;
    
70. 
    
71.   assert((pc_ret != NULL) && (host_addr != NULL) && (request != NULL));
    
72. 
    
73.   //curl_global_init(CURL_GLOBAL_DEFAULT);
    
74.   curl = curl_easy_init();
    
75.   if (!curl)    return 0;
    
76. 
    
77.   //curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
    
78.   curl_easy_setopt(curl, CURLOPT_URL, host_addr);
    
79.   /* Do not do the transfer - only connect to host */
    
80.   curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
    
81.   res = curl_easy_perform(curl);
    
82.   if(CURLE_OK != res) {
    
83.     printf("Error: %s\n", strerror(res));
    
84.     return -1;
    
85.   }
    
86. 
    
87.   /* Extract the socket from the curl handle - we'll need it for waiting.
    
88.    * Note that this API takes a pointer to a 'long' while we use
    
89.    * curl_socket_t for sockets otherwise.
    
90.    */
    
91.   res = curl_easy_getinfo(curl, CURLINFO_LASTSOCKET, &sockextr);
    
92.   if(CURLE_OK != res) {
    
93.     printf("Error: %s\n", curl_easy_strerror(res));
    
94.     return -2;
    
95.   }
    
96. 
    
97.   sockfd = sockextr;
    
98.   /* wait for the socket to become ready for sending */
    
99.   if(!wait_on_socket(sockfd, 0, 60000L)) {
    
100.     printf("Error: timeout.\n");
     
101.     return -3;
     
102.   }
     
103. 
     
104.   /* Send the request. Real applications should check the iolen
     
105.    * to see if all the request has been sent */
     
106.   res = curl_easy_send(curl, request, strlen(request), &iolen);
     
107.   if(CURLE_OK != res) {
     
108.     printf("Error: %s\n", curl_easy_strerror(res));
     
109.     return -4;
     
110.   }
     
111. 
     
112.   /* read the response */
     
113.   char buf[1024];
     
114.   while(1) {
     
115.     wait_on_socket(sockfd, 1, 60000L);
     
116.     res = curl_easy_recv(curl, buf, 1024, &iolen);
     
117. 
     
118.     if(CURLE_OK != res)
     
119.       break;
     
120. 
     
121.     nread = (curl_off_t)iolen;
     
122.   }
     
123.   buf[nread] = '\0';
     
124.   DBG("Received (%" CURL_FORMAT_CURL_OFF_T "), %s\n", nread, buf);
     
125. 
     
126.   /* always cleanup */
     
127.   curl_easy_cleanup(curl);
     
128. 
     
129.   pc_ret = strstr(buf, "\r\n\r\n");
     
130.     if (pc_ret) {
     
131.         pc_ret += 4;
     
132.         DBG("ret = %s\n", pc_ret);
     
133.     }
     
134. 
     
135.   return 1;
     
136. }
     
137. 
     
138. #if (YEELINK == 1)
     
139. int yeelink_create_data(const int device_id, const int sensor_id, const float device_value)
     
140. {
     
141.     char pc_ret[200], request[1024], pc_json[100], pc_time[30], pc_host_file[100], pc_header[100], ret;
     
142.     int len;
     
143. 
     
144.     sprintf(pc_host_file, "v1.0/device/%d/sensor/%d/datapoints", device_id, sensor_id);
     
145.     sprintf(pc_header, "U-ApiKey: %s", YEELINK_API_KEY);
     
146. 
     
147.     get_local_time(pc_time);
     
148.     sprintf(pc_json, "{\"timestamp\":\"%s\",\"value\":%.2f}", pc_time, device_value);
     
149.     len = strlen(pc_json);
     
150. 
     
151.     sprintf(request, "POST /%s HTTP/1.1\r\nHost: %s\r\nAccept: */*\r\n%s\r\nContent-Length: %d\r\nContent-Type: application/x-www-form-urlencoded\r\nConnection: Close\r\n\r\n%s\r\n",
     
152.         pc_host_file, YEELINK_HOST, pc_header, len, pc_json);
     
153.     DBG("request = %s\n", request);
     
154. 
     
155.     ret = connect_cloud(pc_ret, YEELINK_HOST, YEELINK_PORT, request);
     
156. 
     
157.     return(ret);
     
158. }
     
159. #endif
     
160. 
     
161. #if (LEWEI50 == 1)
     
162. //curl --request POST http://www.lewei50.com/api/V1/Gateway/UpdateSensors/01 --data "[{\"Name\":\"T1\",\"Value\":\"23.08\"}]" --header "userkey:36be8ff22f794f1e8a0bee3336eef237"
     
163. int lewei50_create_data(const char *device_id, const float device_value)
     
164. {
     
165.     char pc_ret[200], request[1024], pc_json[100], pc_header[100], ret;
     
166.     int len;
     
167. 
     
168.     assert(device_id != NULL);
     
169. 
     
170.     sprintf(pc_header, "userkey: %s", LEWEI50_USER_KEY);
     
171.     sprintf(pc_json, "[{\"Name\":\"%s\",\"Value\":\"%.2f\"}]", device_id, device_value);
     
172.     len = strlen(pc_json);
     
173. 
     
174.     sprintf(request, "POST /%s HTTP/1.1\r\nHost: %s\r\nAccept: */*\r\n%s\r\nContent-Length: %d\r\nContent-Type: application/x-www-form-urlencoded\r\nConnection: Close\r\n\r\n%s\r\n",
     
175.         LEWEI50_HOST_FILE, LEWEI50_HOST, pc_header, len, pc_json);
     
176.     DBG("request = %s\n", request);
     
177. 
     
178.     ret = connect_cloud(pc_ret, LEWEI50_HOST, LEWEI50_PORT, request);
     
179. 
     
180.     return(ret);
     
181. }
     
182. #endif
     
183. 
     
184. //-------------------------------------------------------------------
     
185. int main(void)
     
186. {
     
187.     float f_value = 15.02;
     
188.     int i_tmp;
     
189. 
     
190.     time_t t;
     
191.   srand((unsigned)time(&t));    //初始化随机种子, 否则随机数不随机
     
192. 
     
193.     i_tmp = rand();
     
194.     i_tmp -= (i_tmp >> 4 << 4);
     
195.   f_value += i_tmp;
     
196. 
     
197. #if (YEELINK == 1)
     
198.     yeelink_create_data(YEELINK_DEVICE_ID, YEELINK_SENSOR_ID, f_value);
     
199. #endif
     
200. 
     
201. #if (LEWEI50 == 1)
     
202.     lewei50_create_data(LEWEI50_DEVICE_ID, f_value);
     
203. #endif
     
204. 
     
205.     return 1;
     
206. }

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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1. OPENWRT = 1
   
2. 
   
3. ifeq ($(OPENWRT), 1)
   
4.     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
   
5.     CFLAGS += -I ~/openwrt-lib/include -L ~/openwrt-lib/lib
   
6.     LFLAGS += -lcurl -lcrypto -lz -lssl
   
7. 
   
8. else
   
9.     CC = gcc
   
10.     LFLAGS += -lcurl
    
11. endif
    
12. 
    
13. CFLAGS += -Wall -O2
    
14. #CFLAGS += -g
    
15. 
    
16. #可执行文件名和相关的obj文件
    
17. APP_BINARY = http_cloud
    
18. SRCS += http_cloud_curl_simple.c
    
19. OBJS = $(SRCS:.c=.o)
    
20. 
    
21. all: APP_FILE
    
22. 
    
23. APP_FILE: $(OBJS)
    
24.     $(CC) $(CFLAGS) $(OBJS) -o $(APP_BINARY) $(LFLAGS)
    
25. 
    
26. .PHONY: clean
    
27. clean:
    
28.     @echo "cleanning project"
    
29.     $(RM) *.a $(OBJS) *~ *.so *.lo $(APP_BINARY)
    
30.     @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......