远程调用servlet

//发起请求、先写发送（out）、然后等待度(in)

URL url = new URL("http://"+strIp+":"+strPort+"/timc/login_returnStreamToClient.do");
   URLConnection con =  url.openConnection();
   con.setUseCaches(true);
   con.setDoOutput(true);
   con.setDoInput(true);
   con.setRequestProperty("Content-type", "application/octest-stream");

   File localFile = new File(localDir.getPath()+File.separatorChar+fileName);
   long startPos = 0;
     if (localFile.exists()) {
     long localFileSize = localFile.length();
     if(localFileSize<=size){
      startPos = localFileSize;
     }
     }else{
     localFile.createNewFile();
     }
    // 设置断点续传的开始位置   （暂时去掉）
   //con.setRequestProperty("RANGE", "bytes=" + startPos);
   ObjectOutputStream os = new ObjectOutputStream(con.getOutputStream());
   os.writeObject(dirName+"#"+fileName);
   os.flush();
   os.close();
   //raf.seek(startPos);
   DataInputStream is = new DataInputStream(con.getInputStream());
   RandomAccessFile raf = new RandomAccessFile(localFile,"rw");
   byte[] b = new byte[1024];
   int nRead; 
   while ((nRead = is.read(b, 0, 1024))!=-1){
             raf.write(b,0,nRead);
   } 
   is.close();
   raf.close();




















//请求接收方、 先处理读、然后再写回去、
HttpServletRequest request = ServletActionContext.getRequest();
HttpServletResponse response = ServletActionContext.getResponse();
String receiveFileName = "";
try {
ObjectInputStream is = new ObjectInputStream(request.getInputStream());
receiveFileName = is.readObject().toString();
is.close();
} catch (Exception e1) {
// TODO Auto-generated catch block
LogUtil.log("获取下级或当前节点传输过来的文件名时出错:",e1);
}
ResourceBundle rb = ResourceBundle.getBundle("config");
File downloadFile = new File(rb.getString("downLoadVersionDir")+File.separatorChar+receiveFileName.replace('#', File.separatorChar));//要下载的文件 
long fileLength = downloadFile.length();//记录文件大小 
long pastLength = 0;//记录已下载文件大小 
int rangeSwitch = 0;//0：从头开始的全文下载；1：从某字节开始的下载（bytes=27000-）；2：从某字节开始到某字节结束的下载（bytes=27000-39000） 
long toLength = 0;//记录客户端需要下载的字节段的最后一个字节偏移量（比如bytes=27000-39000，则这个值是为39000） 
long contentLength = 0;//客户端请求的字节总量 
String rangeBytes = "";//记录客户端传来的形如“bytes=27000-”或者“bytes=27000-39000”的内容  
RandomAccessFile raf = null;//负责读取数据 
OutputStream os = null;//写出数据 
OutputStream out = null;//缓冲 
byte b[] = new byte[1024];//暂存容器 
    if (request.getHeader("Range") != null) {// 客户端请求的下载的文件块的开始字节 
         response.setStatus(javax.servlet.http.HttpServletResponse.SC_PARTIAL_CONTENT); 
         //log.info("request.getHeader(\"Range\")=" + request.getHeader("Range")); 
        rangeBytes = request.getHeader("Range").replaceAll("bytes=", ""); 
            if (rangeBytes.indexOf('-') == rangeBytes.length() - 1) {//bytes=969998336- 
                 rangeSwitch = 1; 
             rangeBytes = rangeBytes.substring(0, rangeBytes.indexOf('-')); 
             pastLength = Long.parseLong(rangeBytes.trim()); 
             contentLength = fileLength - pastLength + 1;//客户端请求的是 969998336 之后的字节 
         } else {//bytes=1275856879-1275877358 
             rangeSwitch = 2; 
             String temp0 = rangeBytes.substring(0,rangeBytes.indexOf('-')); 
             String temp2 = rangeBytes.substring(rangeBytes.indexOf('-') + 1, rangeBytes.length()); 
             pastLength = Long.parseLong(temp0.trim());//bytes=1275856879-1275877358，从第 1275856879 个字节开始下载 
             toLength = Long.parseLong(temp2);//bytes=1275856879-1275877358，到第 1275877358 个字节结束 
             contentLength = toLength - pastLength + 1;//客户端请求的是 1275856879-1275877358  之间的字节 
         } 
     } else {//从开始进行下载 
         contentLength = fileLength;//客户端要求全文下载 
     } 
      
     /**
      * 如果设设置了Content-Length，则客户端会自动进行多线程下载。如果不希望支持多线程，则不要设置这个参数。
      * 响应的格式是:
      * Content-Length: [文件的总大小] - [客户端请求的下载的文件块的开始字节]
      * ServletActionContext.getResponse().setHeader("Content-Length",
      * new Long(file.length() - p).toString());
      */ 
     response.reset();//告诉客户端允许断点续传多线程连接下载,响应的格式是:Accept-Ranges: bytes 
     response.setHeader("Accept-Ranges", "bytes");//如果是第一次下,还没有断点续传,状态是默认的 200,无需显式设置;响应的格式是:HTTP/1.1 200 OK 
     if (pastLength != 0) { 
         //不是从最开始下载, 
         //响应的格式是: 
         //Content-Range: bytes [文件块的开始字节]-[文件的总大小 - 1]/[文件的总大小] 
         //log.info("----------------------------不是从开始进行下载！服务器即将开始断点续传..."); 
         switch (rangeSwitch) { 
             case 1 : {//针对 bytes=27000- 的请求 
                 String contentRange = new StringBuffer("bytes ").append(new Long(pastLength).toString()).append("-").append(new Long(fileLength - 1).toString()).append("/").append(new Long(fileLength).toString()).toString(); 
                 response.setHeader("Content-Range", contentRange); 
                 break; 
             } 
             case 2 : {//针对 bytes=27000-39000 的请求 
                 String contentRange = rangeBytes + "/" + new Long(fileLength).toString(); 
                 response.setHeader("Content-Range", contentRange); 
                 break; 
             } 
             default : { 
                 break; 
             } 
         } 
     } else { 
         //是从开始下载 
        // log.info("----------------------------是从开始进行下载！"); 
     } 
      
     try { 
         //response.addHeader("Content-Disposition", "attachment; filename=\"" + downloadFile.getName() + "\""); 
         response.setContentType("application/octest-stream");// set the MIME type. 
         response.addHeader("Content-Length", String.valueOf(contentLength)); 
         // ByteArrayOutputStream baos = new ByteArrayOutputStream();
          os = new DataOutputStream(response.getOutputStream());
          out = new BufferedOutputStream(os); 
         raf = new RandomAccessFile(downloadFile, "rw"); 
         try { 
             switch (rangeSwitch) { 
                 case 0 : {//普通下载，或者从头开始的下载 
                     //同1 
                 } 
                 case 1 : {//针对 bytes=27000- 的请求 
                     //raf.seek(pastLength);//形如 bytes=969998336- 的客户端请求，跳过 969998336  个字节 
                     int n = 0; 
                     while ((n = raf.read(b, 0, 1024)) != -1) { 
                    out.write(b, 0, n); 
                     } 
                     break; 
                 } 
                 case 2 : {//针对 bytes=27000-39000 的请求 
                     raf.seek(pastLength - 1);//形如 bytes=1275856879-1275877358 的客户端请求，找到第 1275856879 个字节 
                     int n = 0; 
                     long readLength = 0;//记录已读字节数 
                     while (readLength <= contentLength - 1024) {//大部分字节在这里读取 
                         n = raf.read(b, 0, 1024); 
                         readLength += 1024; 
                         out.write(b, 0, n); 
                     } 
                     if (readLength <= contentLength) {//余下的不足 1024 个字节在这里读取 
                         n = raf.read(b, 0, (int)(contentLength - readLength)); 
                         out.write(b, 0, n); 
                     } 
                  
                    raf.seek(pastLength);//形如 bytes=1275856879-1275877358 的客户端请求，找到第 1275856879 个字节 
                  while (raf.getFilePointer() < toLength) { 
                        out.write(raf.read()); 
                     } 
                     break; 
                 } 
                 default : { 
                     break; 
                 } 
             } 
             out.flush(); 
         } catch(IOException ie) { 
             /**
              * 在写数据的时候，
              * 对于 ClientAbortException 之类的异常，
              * 是因为客户端取消了下载，而服务器端继续向浏览器写入数据时，
              * 抛出这个异常，这个是正常的。
              * 尤其是对于迅雷这种吸血的客户端软件，
              * 明明已经有一个线程在读取 bytes=1275856879-1275877358，
              * 如果短时间内没有读取完毕，迅雷会再启第二个、第三个。。。线程来读取相同的字节段，
              * 直到有一个线程读取完毕，迅雷会 KILL 掉其他正在下载同一字节段的线程，
              * 强行中止字节读出，造成服务器抛 ClientAbortException。
              * 所以，我们忽略这种异常
              */ 
             //ignore 
         } 
     } catch (Exception e) { 
        // log.error(e.getMessage(), e); 
     } finally { 
         if (os != null) { 
             try { 
                 os.close(); 
             } catch (IOException e) { 
                // log.error(e.getMessage(), e); 
             } 
         } 
         if (raf != null) { 
             try { 
                 raf.close(); 
             } catch (IOException e) { 
                 //log.error(e.getMessage(), e); 
             } 
         } 
     }