libevent HTTP client 的实现

 　　　　　　 my_conn_ = evhttp_connection_base_new(ev_base_,ev_dns_,host,port);                                                                                  

          struct evhttp_request *http_req;
          http_req = evhttp_request_new(rspCallback,(void *)arg);                        //rspCallback接收消息
          struct evkeyvalq *head = evhttp_request_get_output_headers(http_req);                                                                                 

          evhttp_add_header(head,"User-Agent","My Device");
          evhttp_add_header(head,"Connection","Keep-Alive");
          char buf[];
          snprintf(buf,,"%d",req.terminaltype);
          evhttp_add_header(head,"terminaltype",buf);
          evhttp_add_header(head,"versioninfo",req.version_info.c_str());
          evhttp_add_header(head,"osinfo",req.osinfo.c_str());
          evhttp_add_header(head,"despasswd",req.despasswd.c_str());                                                                                            

          evhttp_add_header(head,"Host",host);                                                                                                                  

          int ret = evhttp_make_request(my_conn_,http_req,EVHTTP_REQ_PUT,"/myurl");
          evhttp_uri_free(uri);