SerialPort: inputStream.read blocks, never return -1

Question

I use javax.comm package to transfer files between two virtual com ports (looped)
Send a file from com3, and receive file from com4, but at reciever side, inputStream.read(buffer) never return eveb though I close the outputstream at the sender.
Here is code:
is: serialPort.getInputStream();
os: serialPort.getOutputStream();
//sender:
//fis: FileInputStream
try {
     int i =0;
     while ((counter=fis.read(buffer)) > 0 ){
          fileSize += counter;
          debugInfo(i + ": "+counter + "bytes read");
          os.write(buffer,0,counter);
          i++;
     debugInfo(fileSize + " bytes read totally");
     os.flush();
     fis.close();
     //close os when no file need transfering
     os.close();
} catch(IOException e) {
     e.printStackTrace();
}file receiver
fos: FileOutStream
try {
     int i =0;
     while ((counter=is.read(buffer)) >0){ //blocks and never return
          counter=is.read(buffer);
           fileSize += counter;
           debugInfo(i + ": "+ counter + " bytes read");
           fos.write(buffer,0, counter);
           i++;
debugInfo(fileSize + " bytes write totally");
fos.flush();
fos.close();
debugInfo("fos closed");
is.close();
} catch(IOException error) {
     error.printStackTrace();
}Anything I have done wrong? or anything better solution? Thanks

Answer 1

oops, sorry for copied wrong codes. Thanks for your remind. The second read was used with while (is.availble()), when I post, I forgot to remove it. You are right, if I have read twice, I will not even get the right file, since I only write every second buffer in.
Here I update the receiver, I can get the whole file correctly, but can't get EOF.
//file receiver
//fos: FileOutStream
try {
     while ((counter=is.read(buffer)) >0){ //blocks and never return
          fileSize += counter;
           fos.write(buffer,0, counter);
fos.flush();
fos.close();
is.close();
} catch(IOException error) {
     error.printStackTrace();
}