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package com.keuin.psmb4j;
import com.keuin.psmb4j.error.IllegalParameterException;
import com.keuin.psmb4j.error.UnsupportedProtocolException;
import com.keuin.psmb4j.util.InputStreamUtils;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.net.SocketException;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
public abstract class BaseClient implements AutoCloseable {
protected final int protocolVersion = 1;
protected final int MAX_CSTRING_LENGTH = 1024;
protected final int DEFAULT_SOCKET_TIMEOUT_MILLIS = 0;
private final String host;
private final int port;
private Socket socket;
protected DataInputStream is;
protected DataOutputStream os;
protected final Object socketWriteLock = new Object();
protected final Object socketReadLock = new Object();
public BaseClient(String host, int port) {
this.host = host;
this.port = port;
}
/**
* Connect to the server.
* This method must be called before sending any other messages,
* and should be called only once.
* If an IO error occurred when doing some operation,
* this client must be reconnected before next operations.
* @throws IOException if a network error occurred
*/
public void connect() throws IOException {
try {
if (this.socket != null) {
throw new IllegalStateException("already connected");
}
this.socket = new Socket(host, port);
this.socket.setSoTimeout(DEFAULT_SOCKET_TIMEOUT_MILLIS);
this.is = new DataInputStream(this.socket.getInputStream());
this.os = new DataOutputStream(this.socket.getOutputStream());
os.writeBytes("PSMB");
os.writeInt(protocolVersion);
os.writeInt(0); // options
os.flush();
var response = InputStreamUtils.readCString(is, MAX_CSTRING_LENGTH);
if (response.equals("UNSUPPORTED PROTOCOL")) {
throw new UnsupportedProtocolException();
} else if (response.equals("OK")) {
var serverOptions = is.readInt();
if (serverOptions != 0) {
throw new IllegalParameterException("Illegal server options: " + serverOptions);
}
}
} catch (IOException ex) {
// failed to connect, reset to initial state
close();
throw ex;
}
}
public void keepAlive() throws IOException {
final var nop = new byte[]{'N', 'O', 'P'};
final var nil = new byte[]{'N', 'I', 'L'};
synchronized (socketReadLock) {
synchronized (socketWriteLock) {
// lock the whole bidirectional communication
os.write(nop);
os.flush();
// wait for a response NIL
var response = InputStreamUtils.readBytes(is, 3);
if (!Arrays.equals(response, nil)) {
throw new RuntimeException("illegal command from server: " +
new String(response, StandardCharsets.US_ASCII));
}
}
}
}
public void disconnect() {
if (os != null) {
try {
os.writeBytes("BYE");
os.flush();
os.close();
} catch (IOException ignored) {
os = null;
}
}
if (is != null) {
try {
is.close();
} catch (IOException ignored) {
is = null;
}
}
if (socket != null) {
try {
socket.close();
} catch (IOException ignored) {
socket = null;
}
}
}
protected void setSocketTimeout(int t) throws SocketException {
this.socket.setSoTimeout(t);
}
@Override
public void close() {
disconnect();
}
}
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