OSS 访问控制，自签名模式，为什么获取token都是nil,导致不能上传文件

get token error: Error Domain=NSURLErrorDomain Code=-1001 "The request timed out." UserInfo={NSUnderlyingError=0x7feaa8d2a090 {Error Domain=kCFErrorDomainCFNetwork Code=-1001 "(null)" UserInfo={_kCFStreamErrorCodeKey=-2102, _kCFStreamErrorDomainKey=4}}, NSErrorFailingURLStringKey=http://www.201494.com:8080/tsjb/ossServer, NSErrorFailingURLKey=http://www.201494.com:8080/tsjb/ossServer, _kCFStreamErrorDomainKey=4, _kCFStreamErrorCodeKey=-2102, NSLocalizedDescription=The request timed out.}
2016-03-08 13:54:54.865 oss_ios_demo[1950:113526] [fg0,255,0;get federation token, but after -1457416494.865366 second it would be expired[;
2016-03-08 13:54:54.866 oss_ios_demo[1950:113526] copy error, error: Error Domain=com.aliyun.oss.clientError Code=1 "(null)" UserInfo={ErrorMessage=Can't get a federation token}