Java sending and receiving file byte over sockets

Question

I am trying to develop a very simple client   server where the client converts a file to bytes  sends it to the server  and then converts the bytes back in to a file    Currently the program just creates an empty file  I m not a fantastic Java developer so any help much appreciated   This is the server part that receives what the client sends   ServerSocket serverSocket   null       serverSocket   new ServerSocket 4444         Socket socket   null      socket   serverSocket accept         DataOutputStream out   new DataOutputStream new BufferedOutputStream socket getOutputStream          DataInputStream in   new DataInputStream new BufferedInputStream socket getInputStream          byte   bytes   new byte 1024        in read bytes       System out println bytes        FileOutputStream fos   new FileOutputStream  C   test2 xml        fos write bytes     And here is the client part  Socket socket   null      DataOutputStream out   null      DataInputStream in   null      String host    127 0 0 1             socket   new Socket host  4444       out   new DataOutputStream new BufferedOutputStream socket getOutputStream          in   new DataInputStream new BufferedInputStream socket getInputStream           File file   new File  C   test xml          InputStream is   new FileInputStream file          Get the size of the file     long length   file length        if  length  gt  Integer MAX VALUE            System out println  File is too large               byte   bytes   new byte  int  length          out write bytes       System out println bytes        out close        in close        socket close

User · Answer

To avoid the limitation of the file size   which can cause the Exception java lang OutOfMemoryError to be thrown when creating an array of the file size byte   bytes   new byte  int  length    instead we could do       byte   bytearray   new byte 1024 16       FileInputStream fis   null      try            fis   new FileInputStream file           OutputStream output  socket getOututStream            BufferedInputStream bis   new BufferedInputStream fis            int readLength   -1          while   readLength   bis read bytearray    gt  0                output write bytearray  0  readLength                      bis close            output close              catch Exception ex             ex printStackTrace            Excuse the poor exception handling

User · Answer

Thanks for the help  I ve managed to get it working now so thought I would post so that the others can use to help them  Server  public class Server       public static void main String   args  throws IOException           ServerSocket serverSocket   null           try               serverSocket   new ServerSocket 4444             catch  IOException ex                System out println  quot Can t setup server on this port number   quot                       Socket socket   null          InputStream in   null          OutputStream out   null                   try               socket   serverSocket accept              catch  IOException ex                System out println  quot Can t accept client connection   quot                               try               in   socket getInputStream              catch  IOException ex                System out println  quot Can t get socket input stream   quot                       try               out   new FileOutputStream  quot M   test2 xml quot              catch  FileNotFoundException ex                System out println  quot File not found   quot                       byte   bytes   new byte 16 1024            int count          while   count   in read bytes    gt  0                out write bytes  0  count                      out close            in close            socket close            serverSocket close             and the Client  public class Client       public static void main String   args  throws IOException           Socket socket   null          String host    quot 127 0 0 1 quot            socket   new Socket host  4444                    File file   new File  quot M   test xml quot               Get the size of the file         long length   file length            byte   bytes   new byte 16   1024           InputStream in   new FileInputStream file           OutputStream out   socket getOutputStream                     int count          while   count   in read bytes    gt  0                out write bytes  0  count                      out close            in close            socket close

User · Answer

Rookie  if you want to write a file to server by socket  how about using fileoutputstream instead of dataoutputstream  dataoutputstream is more fit for protocol-level read-write  it is not very reasonable for your code in bytes reading and writing  loop to read and write is necessary in java io  and also  you use a buffer way  flush is necessary  here is a code sample  http   www rgagnon com javadetails java-0542 html

User · Answer

Adding up on EJP s answer  use this for more fluidity  Make sure you don t put his code inside a bigger try catch with more code between the  read and the catch block  it may return an exception and jump all the way to the outer catch block  safest bet is to place EJPS s while loop inside a try catch  and then continue the code after it  like    int count  byte   bytes   new byte 4096   try       while   count   is read bytes    gt  0            System out println count           bos write bytes  0  count           catch   Exception e           It will land here          Then continue from here   EDIT   This happened to me cuz I didn t realize you need to put socket shutDownOutput   if it s a client-to-server stream   Hope this post solves any of your issues

User · Answer

The correct way to copy a stream in Java is as follows   int count  byte   buffer   new byte 8192      or 4096  or more while   count   in read buffer    gt  0      out write buffer  0  count       Wish I had a dollar for every time I ve posted that in a forum

User · Answer

Here is the server Open a stream to the file and send it overnetwork  import java io BufferedInputStream  import java io File  import java io FileInputStream  import java io IOException  import java io OutputStream  import java net ServerSocket  import java net Socket   public class SimpleFileServer      public final static int SOCKET PORT   5501    public final static String FILE TO SEND    file txt      public static void main  String    args   throws IOException       FileInputStream fis   null      BufferedInputStream bis   null      OutputStream os   null      ServerSocket servsock   null      Socket sock   null      try         servsock   new ServerSocket SOCKET PORT         while  true            System out println  Waiting               try             sock   servsock accept              System out println  Accepted connection       sock                send file           File myFile   new File  FILE TO SEND             byte    mybytearray    new byte   int myFile length               fis   new FileInputStream myFile             bis   new BufferedInputStream fis             bis read mybytearray 0 mybytearray length             os   sock getOutputStream              System out println  Sending     FILE TO SEND         mybytearray length     bytes               os write mybytearray 0 mybytearray length             os flush              System out println  Done               catch  IOException ex              System out println ex getMessage      An Inbound Connection Was Not Resolved                       finally             if  bis    null  bis close              if  os    null  os close              if  sock  null  sock close                                finally         if  servsock    null          servsock close                  Here is the client Recive the file being sent overnetwork  import java io BufferedOutputStream  import java io FileOutputStream  import java io IOException  import java io InputStream  import java net Socket   public class SimpleFileClient      public final static int SOCKET PORT   5501    public final static String SERVER    127 0 0 1     public final static String        FILE TO RECEIVED    file-rec txt      public final static int FILE SIZE   Integer MAX VALUE     public static void main  String    args   throws IOException       int bytesRead      int current   0      FileOutputStream fos   null      BufferedOutputStream bos   null      Socket sock   null      try         sock   new Socket SERVER  SOCKET PORT         System out println  Connecting                 receive file       byte    mybytearray    new byte  FILE SIZE         InputStream is   sock getInputStream          fos   new FileOutputStream FILE TO RECEIVED         bos   new BufferedOutputStream fos         bytesRead   is read mybytearray 0 mybytearray length         current   bytesRead         do            bytesRead               is read mybytearray  current   mybytearray length-current             if bytesRead  gt   0  current    bytesRead          while bytesRead  gt  -1          bos write mybytearray  0   current         bos flush          System out println  File     FILE TO RECEIVED               downloaded      current     bytes read               finally         if  fos    null  fos close          if  bos    null  bos close          if  sock    null  sock close

[java] Java sending and receiving file (byte[]) over sockets

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