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

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

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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......