Linux 下C使用XML传递消息（字符串）

在linux下经常要进行socket通信，而数据流多采用目前流行的xml格式，这就会有两个用的比较多的功能：
1、接收端将收到的字符串转换成xml格式的数据；
2、发送端将xml格式的数据转换成字符串发送。

运用libxml2组件进行上述操作实际上是xmlDocPtr和xmlChar两种类型之间的转换。

1. xmlDocPtr -> xmlChar
xmlDocPtr doc;
xmlChar *xmlbuff;
int buffersize;
xmlDocDumpFormatMemory(doc, &xmlbuff, &buffersize, 1);
2. xmlChar -> xmlDocPtr
xmlDocPtr doc;
char * cData;
doc = xmlParseMemory(docname, strlen(cData)+1);
怎样把xmlChar转换成char就无须多讲了，直接用（char*）强行转换也行。

(以上，转自http://hi.baidu.com/dante300/blog/item/b0962f51e472261d0cf3e3ad.html)

下面的例子，srv端等待6601端口的数据，并使用XML解析，取得其中的name和age项，并打印到终端

client端读取一个XML文件，并把读取的数据转换为字符串，向服务端的端口发送

[cpp] view plaincopyprint?

1. /*srv.c By ksir in 2011-10-14*/
2. #include <stdio.h>
3. #include <stdlib.h>
4. #include <string.h>
5. #include <ctype.h>
6. #include <sys/socket.h>
7. #include <netinet/in.h>
8. #include <arpa/inet.h>
9. #include <libxml/parser.h>
10. #include <libxml/xmlmemory.h>
12. #define MAXLINE 80
13. int port = 6601; /*Port of socket*/
15. /*parse XML and show content of 'name','age'*/
16. int parseXML(xmlDocPtr tmpdoc)
17. {
18. //printf("This is in parseXML\n");
19. xmlNodePtr curNode; /*Keep node of the xml tree*/
20. xmlChar *szKey;
22. /*Get the root Node from tmpdoc*/
23. curNode = xmlDocGetRootElement(tmpdoc);
24. /*check the content of the document*/
25. if (NULL == curNode)
26. {
27. xmlFreeDoc(tmpdoc);
28. return -3;
29. }
31. /*Check the type of the root element*/
32. if(xmlStrcmp(curNode->name,BAD_CAST"n"))
33. {
34. printf("Document of the wrong type");
35. xmlFreeDoc(tmpdoc);
36. return -4;
37. }
38. curNode = curNode->xmlChildrenNode;
39. xmlNodePtr propNpdePtr =curNode;
40. while (curNode != NULL)
41. {
42. /*compare element nodes,show the content*/
43. if( !(xmlStrcmp(curNode->name,(const xmlChar *)"name")))
44. {
45. szKey = xmlNodeGetContent(curNode);
46. printf("name:%s\n",szKey);
47. xmlFree(szKey);
48. }
49. else if( !(xmlStrcmp(curNode->name,(const xmlChar *)"age")))
50. {
51. printf("Age:%s\n",xmlNodeGetContent(curNode));
52. }
53. /*traverse*/
54. curNode = curNode->next;
55. }
56. xmlFreeDoc(tmpdoc);
57. return 0;
58. }
60. int main(void)
61. {
62. struct sockaddr_in sin;
63. struct sockaddr_in rin;
64. int sock_fd;
65. int address_size;
66. char buf[MAXLINE];
67. char str[INET_ADDRSTRLEN];
68. int len;
69. int n;
71. xmlDocPtr doc;
73. bzero(&sin, sizeof(sin));
74. sin.sin_family = AF_INET;
75. sin.sin_addr.s_addr = INADDR_ANY;
76. sin.sin_port = htons(port);
79. sock_fd = socket(AF_INET, SOCK_DGRAM, 0);
80. if (-1 == sock_fd)
81. {
82. perror("call to socket");
83. exit(1);
84. }
85. n = bind(sock_fd, (struct sockaddr *)&sin, sizeof(sin));
86. if (-1 == n)
87. {
88. perror("call to bind");
89. exit(1);
90. }
92. while(1)
93. {
94. address_size = sizeof(rin);
95. n = recvfrom(sock_fd,buf,MAXLINE,0,(struct sockaddr *)&rin,
96. &address_size);
97. if (-1 == n)
98. {
99. perror("call to recvfrom.\n");
100. exit(1);
101. }
102. // printf("you ip is %s at port %d:%s\n",
103. // inet_ntop(AF_INET, &rin.sin_addr,str,sizeof(str)),
104. // ntohs(rin.sin_port),(char *)buf);
106. /*transfer buf to xml*/
107. doc = xmlParseMemory((char *)buf,strlen(buf)+1);
108. if (NULL == doc)
109. {
110. printf("xmlParseMemory fail\n");
111. return -2;
112. }
113. parseXML(doc);
114. }
115. return 0;
116. }

客户端代码：

[cpp] view plaincopyprint?

1. /*Client.c by ksir in 2011-10-14*/
3. #include<stdio.h>
4. #include<string.h>
5. #include<stdlib.h>
6. #include<sys/types.h>
7. #include<unistd.h>
8. #include<sys/socket.h>
9. #include<linux/in.h>
10. #include <libxml/parser.h>
11. #include <libxml/xmlmemory.h>
14. int main(int argc,char *argv[])
15. {
16. if(argc<2){
17. printf("Please input a file !\n");
18. exit(0);
19. }
20. int sock;
21. struct sockaddr_in toAddr;
22. struct sockaddr_in fromAddr;
24. unsigned int fromLen;
25. char recvBuffer[128];
26. sock=socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP);
27. if(sock<0){
28. printf("Sock failed!\n");
29. exit(1);
30. }
32. memset(&toAddr,0,sizeof(toAddr));
34. toAddr.sin_family=AF_INET;
35. toAddr.sin_addr.s_addr=inet_addr("10.11.1.88");
36. toAddr.sin_port=htons(6601);
38. /*Get the xmlfile and parse into string*/
39. xmlDocPtr doc; /*file descriptor of the xml*/
40. xmlChar *xmlbuf;
41. char *szDocName;
42. int buffersize;
44. szDocName = argv[1];
46. /*Open with GB2312*/
47. doc = xmlReadFile(szDocName,"GB2312",XML_PARSE_RECOVER);
48. xmlDocDumpFormatMemory(doc, &xmlbuf, &buffersize, 1);
49. printf((char *) xmlbuf);
51. while(1)
52. {
53. sleep(1);
55. if(sendto(sock,xmlbuf,strlen(xmlbuf)+1,0,(struct sockaddr *)&toAddr,sizeof(toAddr)) == -1){
56. printf("Sendto failed!\n");
57. exit(2);
58. }
60. printf("OK!\n");
61. }
62. close(sock);
63. }

使用的XML文件：

[html] view plaincopyprint?

1. <n>
2. <name>
3. ksir
4. </name>
5. <age>
6. 18
7. </age>
8. </n>

使用libxml2库的.c文件的编译：

gcc -o srv ser.c -I /usr/include/libxml2/ -L /usr/local/lib -lxml2

LIBXML2的学习地址：http://www.xmlsoft.org/html/libxml-tree.html