Method read is blocked!!!!!!!

Question

I programmed a server in JSE and I like to do a client in J2ME, my problem is the server send a few data, the client receives that data but in the last call to read() method it blocks!!!!!!, it doesn't throws any exception.
My server code:
//client is a Socket
input = client.getInputStream();
output = client.getOutputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(input));
PrintWriter ps = new PrintWriter(output, true);
//BufferedWriter bw=new BufferedWriter(new OutputStreamWriter(output));
ps.println("?version");
String version = br.readLine();
System.out.println(version);
br.close();
ps.close();
client.close();
Client code (J2ME):
SocketConnection connection = (SocketConnection) Connector.open("socket://myhost:49900");
InputStream in = connection.openInputStream();
OutputStream out = connection.openOutputStream();
char com = (char) in.read();
StringBuffer comand = new StringBuffer();
StringBuffer error = new StringBuffer();
switch (com) {
case '?':
char ch = 0;
int c=0;
//here receives "version\r\n" and after this the read() method blocks don't return -1
for (int i = in.read(), j = 0; i != -1; i = in.read(), j++) {
System.out.println((char) i + " " + i);
comand.append((char) i);
break;
case '!':
for (int i = in.read(), j = 0; i != -1; i = in.read(), j++) {
error.append((char) i);
break;
System.out.println(comand.toString().trim());
if (comand.toString().equals("version")) {
out.write((version + "\r\n").getBytes());
System.out.println("Version enviada");
}

Answer 1

I see the problem, you are expecting in.read to return -1 when no data is available. As per the documentation, the read method returns -1 when the stream is closed, not when data is unavailable. The stream is not closed and hence the client is blocked (I assumed you already know that the read operation is blocking operation).
At your server side after you write the version to the outputstream using Printwriter (using statement ps.println("?version");), you are expecting input from client. Your client is already blocked, so its not sending out any data. Hence the server is also blocked.
I would suggest have something in your protocol which tells you that server has sent has its bytes and now its client side. For example, server sends out length of the message in lets say first 2 bytes and then the actual message. That way your client implementation will always know how many bytes to expect from the server.
Or use in.available() - which returns the number of bytes that can be read from this input stream without blocking.
Hope this will help you solve your problem.
Atul