CODEWITHSUNDEEP
javaserversocket
user1612078
user1612078

Reputation: 585

Not receiving any further messages after receiving a file over socket

I am sending a file over socket from client to server. Thats working fine. But once a file is received, server program is not receiving any further messages. Its all receiving is null. Here is the client-server code.

Client:

main(...){
  Socket sock = new Socket("127.0.0.1", 12345);
  File file = new File("file.txt");
  byte[] mybytearray = new byte[(int) file.length()];
    BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file));
    bis.read(mybytearray, 0, mybytearray.length);
    OutputStream os = sock.getOutputStream();
    os.write(mybytearray, 0, mybytearray.length);

    PrintWriter out = new PrintWriter(os, true);
    out.println("next message");

    //closing here all streams and socket
}

Server:

main(...){
 ServerSocket servsock = new ServerSocket(12345);
    while (true) {
        Socket sock = servsock.accept();
        byte[] mybytearray = new byte[1024];
        InputStream is = sock.getInputStream();
        Scanner scan1 = new Scanner(is);
        FileOutputStream fos = new FileOutputStream("myfile.txt");
        BufferedOutputStream bos = new BufferedOutputStream(fos);
        int bytesRead = is.read(mybytearray, 0, mybytearray.length);
        bos.write(mybytearray, 0, bytesRead);
        bos.close();
        fos.close();
        //Till here works fine, and file is successfully received.

        //Below is the code to receive next message. 
        //Unfortunately it is not working 
        BufferedReader input = new BufferedReader(new InputStreamReader(is));
        String line = input.readLine();
        System.out.println(line); //prints null, Whats the reason?
   }
}

Upvotes: 1

Views: 47

Answers (2)

WillShackleford
WillShackleford

Reputation: 7018

This is an example that assumes it is a file then a line of text. In both cases I send the length first so it can just be dealt with as byte arrays.

Server:

ServerSocket servsock = new ServerSocket(12345);
while (true) {
    Socket sock = servsock.accept();
    try (DataInputStream dis = new DataInputStream(sock.getInputStream())) {
        int len = dis.readInt();
        byte[] mybytearray = new byte[len];
        dis.readFully(mybytearray);
        try (FileOutputStream fos = new FileOutputStream("myfile.txt")) {
            fos.write(mybytearray);
        }
        len = dis.readInt();
        mybytearray = new byte[len];
        dis.readFully(mybytearray);
        String line = new String(mybytearray);
        System.out.println("line = " + line);
    }
}

Client:

Socket sock = new Socket("127.0.0.1", 12345);
File file = new File("file.txt");
byte[] mybytearray = new byte[(int) file.length()];
DataInputStream dis = new DataInputStream(new FileInputStream(file));
dis.readFully(mybytearray);
try(DataOutputStream os = new DataOutputStream(sock.getOutputStream())) {
    os.writeInt(mybytearray.length);
    os.write(mybytearray, 0, mybytearray.length);
    String nextMessage = "next message\n";
    byte message[] = nextMessage.getBytes();
    os.writeInt(message.length);
    os.write(message, 0, message.length);
}

Upvotes: 1

Peter Lawrey
Peter Lawrey

Reputation: 533820

The basic problem is you assume a) your file is exactly 1024 bytes long when you read. b) when you attempt to read you get all the data in one go. The minimum is 1 byte even if you wrote much more.

I suggest you

  • send the length with the file so you know how much to read.
  • you chose either binary or text and only do one or the other.

Upvotes: 1

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