Why can't streaming connect to the Java socket client? - apache-spark

Question

I am studying Spark streaming to process real time data, and I built the example wordCount of spark streaming, and I can run the example after:
/bin/run-example org.apache.spark.streaming.examples.JavaNetworkWordCount local[2] localhost 9999
And if I run nc -L -p 9999 in another terminal, then I can type letters in this terminal, and the example can receive the letters and give the right result.
But I developed a Java socket client to send content to 9999 port - why can't the example receive it? I think the example just monitor the 9999 port, and receive anything from the port.
Here is the Java code:
File file = new File("D:\\OutputJson.dat");
long l = file.length();
socket = new Socket();
boolean connected = false;
while (!connected) {
//not stop until send successful
try {
socket.connect(new InetSocketAddress("localhost", 9999));
connected = true;
System.out.println("connected success!");
} catch (Exception e) {
e.printStackTrace();
System.out.println("connected failed!");
Thread.sleep(5000);
}
}
dos = new DataOutputStream(socket.getOutputStream());
fis = new FileInputStream(file);
sendBytes = new byte[1024];
while ((length = fis.read(sendBytes, 0, sendBytes.length)) > 0) {
sumL += length;
System.out.println("sent:" + ((sumL / l) * 100) + "%");
dos.write(sendBytes, 0, length);
dos.flush();
}
if (sumL == l) {
bool = true;
}
This Java function is always returning the following error:
java.net.SocketException: Socket closed
I have developed another Java class to receive the data from this sending socket, and it works fine, why the can't spark receive with this one?

Answer 1

From memory I think I used a ServerSocket. The code was something like:
public void sendMsg(String msg) throws IOException {
ServerSocket serverSocket = null;
Socket clientSocket = null;
try {
serverSocket = new ServerSocket(port);
clientSocket = serverSocket.accept();
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
out.write(msg);
out.flush();
out.close();
} finally {
try {
clientSocket.close();
serverSocket.close();
} finally {
clientSocket = null;
serverSocket = null;
}
}
}