對(duì)于基于socket的inputstream而言，不像基于文件的流，除非socket關(guān)閉，否則是不會(huì)有EOF這個(gè)概念的（-1）

int bytesRead = 0;
            int bytesToRead = pageLength;

            while (bytesRead < bytesToRead) {
                int result = dis.read(buffer, bytesRead+4, bytesToRead    - bytesRead);
                if (result == -1)
                    break;
                bytesRead += result;
            }