Large file transfer problems over client/server socket

Question

Hi,
I wrote a simple chat problem in which I can send files from client to client. The problem is when I send large files over 101 MB the transfer freezes. I do not even get any error mesages in the console. The files I am sending are of any type (Ex mp3, movies, etc...). I am serializing the data into a "byteArray[packetSize]" and sending the file packet by packet until the whole file has been sent, and reconstructed on the other side. The process works perfectly for files smaller than 101MB, but for some reason freezes after that if the file is larger. I have read many forums and there aren't too many solutions out there. I made sure to use the .reset() method to reset my ObjectOutputStream each time I write to it.
Here's my file sending code:
byte[] byteArray = new byte[defaultPacketSize];
numPacketsRequired = Math.ceil(fileSize / defaultPacketSize);
try {
int i = 0;
reader = new FileInputStream(filePath);
while (reader.available() > 0) {
if (reader.available() < defaultPacketSize) {
byte[] lastPacket = new byte[reader.available()];
reader.read(lastPacket);
try {
if (socket == null || output == null) {
throw new SocketException("socket does not exist");
output.writeObject(lastPacket);
output.reset();
output.writeObject("DONE");
output.reset();
output.close();
socket.close();
catch (Exception e) {
System.out.println("Exception ***: " + e);
output.close();
socket.close();
else {
reader.read(byteArray);
try {
if (socket == null || output == null) {
throw new SocketException("socket does not exist");
output.writeObject(byteArray);
output.reset();
catch (Exception e) {
System.out.println("Exception ***: " + e);
output.close();
socket.close();
reader.close();
catch (Exception e) {
System.out.println("COULD NOT READ PACKET");
Here's my file receiving code:
try {
// The message from the client
Object streamInput;
FileOutputStream writer;
byte[] packet;
while (true) {
streamInput = input.readObject();
if (streamInput instanceof byte[]) {
packet = (byte[]) streamInput;
try {
writer = new FileOutputStream(outputPath, true);
writer.write(packet); //Storing the bytes on file
writer.close();
catch (Exception e) {
System.out.println("Exception: " + e);
else if (streamInput.equals("DONE")) {
socket.close();
input.close();
break;
catch (Exception e) {
I'm looking for any way I can possibly send large files from client to client without having it freeze. Are there any better file transfer ways other than socket? I don't really want FTP. I think I want to keep it HTTP.
Any suggestions would be helpful.Thanks!
Evan

Answer 1

I've taken a better look a the code you posted, and
there is one problem with the receiving code. You
keep repeatedly opening and closing the
FileOutputStream. This is not going to be efficient
as the file will keep needing to be positioned to its
end.Yes sorry I did change that code so that it leaves the file open until completely done writing. Basically I have a progress bar that records how far along in the writing process the client is, and when the progress bar reaches 100%, meaning the file is complete, the file.close() method is invoked. Sorry about that.
I also ran some memory tests using the "Runtime.getRuntime().totalMemory()", and "Runtime.getRuntime().freeMemory()" methods. I put these methods inside the loop where I read in the file and send it to the client. here's the output:
Sender's free memory: 704672
File reader read 51200 bytes of data.
767548 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 702968
File reader read 51200 bytes of data.
716348 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 701264
File reader read 51200 bytes of data.
665148 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 699560
File reader read 51200 bytes of data.
613948 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 697856
File reader read 51200 bytes of data.
562748 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 696152
File reader read 51200 bytes of data.
511548 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 694448
File reader read 51200 bytes of data.
460348 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 692744
File reader read 51200 bytes of data.
409148 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 691040
File reader read 51200 bytes of data.
357948 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 689336
File reader read 51200 bytes of data.
306748 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 687632
File reader read 51200 bytes of data.
255548 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 685928
File reader read 51200 bytes of data.
204348 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 684224
File reader read 51200 bytes of data.
153148 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 682520
File reader read 51200 bytes of data.
101948 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 680816
File reader read 51200 bytes of data.
50748 left to read.
Sender's runtime memory: 2818048
Sender's free memory: 679112
File reader read 50748 bytes of data.
0 left to read.
Creating last packet of size: 50748
Last packet size after setting it equal to byteArray: 50748
Here's the memory stats from the receiver:
Receiver's free memory: 639856
Receiver's total memory: 2842624
Receiver's free memory: 638920
Receiver's total memory: 2842624
Receiver's free memory: 637984
Receiver's total memory: 2842624
Receiver's free memory: 637048
Receiver's total memory: 2842624
Receiver's free memory: 636112
Receiver's total memory: 2842624
Receiver's free memory: 635176
Receiver's total memory: 2842624
Receiver's free memory: 634240
Receiver's total memory: 2842624
Receiver's free memory: 633304
Receiver's total memory: 2842624
Receiver's free memory: 632368
Receiver's total memory: 2842624
Receiver's free memory: 631432
Receiver's total memory: 2842624
Receiver's free memory: 630496
Receiver's total memory: 2842624
Receiver's free memory: 629560
Receiver's total memory: 2842624
Receiver's free memory: 628624
Receiver's total memory: 2842624
Receiver's free memory: 627688
Receiver's total memory: 2842624
Receiver's free memory: 626752
Receiver's total memory: 2842624
Receiver's free memory: 625816
Receiver's total memory: 2842624
Receiver's free memory: 624880
Receiver's total memory: 2842624
Receiver's free memory: 623944
Receiver's total memory: 2842624
Receiver's free memory: 623008
Receiver's total memory: 2842624
Receiver's free memory: 622072
Receiver's total memory: 2842624
Receiver's free memory: 621136
Receiver's total memory: 2842624
Receiver's free memory: 620200
Receiver's total memory: 2842624
Receiver's free memory: 619264
Receiver's total memory: 2842624
Receiver's free memory: 618328
Receiver's total memory: 2842624
Receiver's free memory: 617392
Receiver's total memory: 2842624
Receiver's free memory: 616456
Receiver's total memory: 2842624
Receiver's free memory: 615520
Receiver's total memory: 2842624
Receiver's free memory: 614584
this is just a sample of both receiver and sender's stats. Everything appears to be fine! Hope this message post isn't too long.
Thanks!