请高手解释一下Java错误跟踪

Exception:  java.net.SocketTimeoutException: Read timed out
Stack Trace follows:
java.net.SocketTimeoutException: Read timed out
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at HTTPClient.BufferedInputStream.fillBuff(BufferedInputStream.java:172)
at HTTPClient.BufferedInputStream.read(BufferedInputStream.java:110)
at HTTPClient.StreamDemultiplexor.read(StreamDemultiplexor.java:273)
at HTTPClient.RespInputStream.read(RespInputStream.java:155)
at HTTPClient.RespInputStream.read(RespInputStream.java:115)
at HTTPClient.Response.readResponseHeaders(Response.java:971)
at HTTPClient.Response.getHeaders(Response.java:693)
at HTTPClient.Response.getStatusCode(Response.java:263)
at HTTPClient.RetryModule.responsePhase1Handler(RetryModule.java:83)
at HTTPClient.HTTPResponse.handleResponse(HTTPResponse.java:724)
at HTTPClient.HTTPResponse.getStatusCode(HTTPResponse.java:190)
at org.smsbroker.utils.HttpConnectionRequest.httpConnection(HttpConnectionRequest.java:320)
at org.smsbroker.utils.HttpConnectionRequest.connection(HttpConnectionRequest.java:199)
at org.smsbroker.sms.SmsRequestCache.getURLData(SmsRequestCache.java:78)
at org.smsbroker.sms.SmsRequestCache.getData(SmsRequestCache.java:136)
at org.smsbroker.sms.smsproxy.getUrlData(smsproxy.java:629)
at org.smsbroker.sms.smsrequest.run(smsrequest.java:369)
at java.lang.Thread.run(Thread.java:595)