Create a basic Connection class

lib/src/main/java/io/github/lonamiwebs/overgram/Overgram.java

@@ -1,6 +1,14 @@
 package io.github.lonamiwebs.overgram;
 
+import io.github.lonamiwebs.overgram.network.connection.Connection;
+import io.github.lonamiwebs.overgram.network.connection.TcpFull;
+
+import java.io.IOException;
+
 public class Overgram {
-    public static void main(final String... args) {
+    public static void main(final String... args) throws IOException {
+        final Connection connection = new TcpFull();
+        connection.connect("149.154.167.91", 443);
+        connection.disconnect();
     }
 }

lib/src/main/java/io/github/lonamiwebs/overgram/network/TcpClient.java

@@ -0,0 +1,46 @@
+package io.github.lonamiwebs.overgram.network;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.Socket;
+
+public class TcpClient {
+
+    private Socket socket;
+
+    public void connect(final String ipAddress, final int port) throws IOException {
+        socket = new Socket(ipAddress, port);
+    }
+
+    public void close() {
+        try {
+            socket.close();
+        } catch (IOException ignored) {
+        }
+    }
+
+    public byte[] read(final int length) throws IOException {
+        final InputStream in = socket.getInputStream();
+        final byte[] result = new byte[length];
+
+        int index = 0;
+        while (true) {
+            final int count = in.read(result, index, result.length - index);
+            if (count == -1) {
+                throw new IOException("Connection closed");
+            }
+
+            index += count;
+            if (index == result.length) {
+                return result;
+            }
+        }
+    }
+
+    public void write(final byte[] bytes) throws IOException {
+        final OutputStream out = socket.getOutputStream();
+        out.write(bytes);
+        out.flush();
+    }
+}

lib/src/main/java/io/github/lonamiwebs/overgram/network/connection/Connection.java

@@ -0,0 +1,13 @@
+package io.github.lonamiwebs.overgram.network.connection;
+
+import java.io.IOException;
+
+public abstract class Connection {
+    public abstract void connect(final String ipAddress, final int port) throws IOException;
+
+    public abstract void disconnect();
+
+    public abstract void send(final byte[] data) throws IOException;
+
+    public abstract byte[] recv() throws IOException;
+}

lib/src/main/java/io/github/lonamiwebs/overgram/network/connection/TcpFull.java

@@ -0,0 +1,59 @@
+package io.github.lonamiwebs.overgram.network.connection;
+
+import io.github.lonamiwebs.overgram.network.TcpClient;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.util.zip.CRC32;
+
+public class TcpFull extends Connection {
+
+    private final TcpClient client;
+    private int counter;
+
+    public TcpFull() {
+        client = new TcpClient();
+    }
+
+    @Override
+    public void connect(final String ipAddress, final int port) throws IOException {
+        client.connect(ipAddress, port);
+        counter = 0;
+    }
+
+    @Override
+    public void disconnect() {
+        client.close();
+    }
+
+    @Override
+    public void send(final byte[] data) throws IOException {
+        final int length = data.length + 12;
+
+        final ByteBuffer buffer = ByteBuffer.allocate(length);
+        buffer.order(ByteOrder.LITTLE_ENDIAN);
+
+        buffer.putInt(length);
+        buffer.putInt(counter);
+        buffer.put(data);
+
+        final CRC32 crc32 = new CRC32();
+        crc32.update(buffer.array(), 0, length - 4);
+        buffer.putInt((int) crc32.getValue());
+
+        client.write(buffer.array());
+        ++counter;
+    }
+
+    @Override
+    public byte[] recv() throws IOException {
+        final ByteBuffer buffer = ByteBuffer.wrap(client.read(8));
+        final int length = buffer.getInt();
+        final int seq = buffer.getInt();
+        final byte[] body = client.read(length - 12);
+        final int crc = ByteBuffer.wrap(client.read(4)).getInt();
+        // TODO Check crc
+        return body;
+    }
+}