1 files changed, 126 insertions, 0 deletions
diff --git a/src/main/java/com/keuin/psmb4j/BaseClient.java b/src/main/java/com/keuin/psmb4j/BaseClient.java
new file mode 100644
index 0000000..3c5cf08
--- /dev/null
+++ b/src/main/java/com/keuin/psmb4j/BaseClient.java
@@ -0,0 +1,126 @@
+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();
+    }
+}