diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..bea94fe
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,21 @@
+# Dual: a simple manager for custom hostnames
+#
+# Copyright (C) 2021 luca0N!
+#
+# This program is free software: you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation, either version 3 of the License, or (at your option) any later
+# version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program. If not, see <https://www.gnu.org/licenses/>.
+#
+# Contact me by e-mail via <luca0n [at] luca0n [dot] com>.
+
+Dual.jar:
+	javac -d build/ -classpath src/ src/com/luca0n/dual/config/*.java src/com/luca0n/dual/common/*.java
+	jar -cfve Dual.jar com.luca0n.dual.common.Dual -C build/ .
diff --git a/cfg/gen.cfg b/cfg/gen.cfg
new file mode 100644
index 0000000..646b799
--- /dev/null
+++ b/cfg/gen.cfg
@@ -0,0 +1,52 @@
+# Dual: a simple manager for custom hostnames
+#
+# Copyright (C) 2021 luca0N!
+#
+# This program is free software: you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation, either version 3 of the License, or (at your option) any later
+# version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program. If not, see <https://www.gnu.org/licenses/>.
+#
+# Contact me by e-mail via <luca0n [at] luca0n [dot] com>.
+
+# ####    ##  ##   ##   ##
+# ##  ##  ##  ## ##  ## ##
+# ##  ##  ##  ## ##  ## ##      configuration
+# ##  ##  ##  ## ###### ##      file
+# ##  ##  ##  ## ##  ## ##
+# ####      ##   ##  ## #####
+#
+# Configuration file for Dual.
+#
+# Lines that begin with the "#" character are comments.  Everything written in a
+# line after "#" is considered a comment.  Comments are ignored.
+[Dual]
+# Put instructions that should be sent to Dual here.
+
+# Provide the path to the hosts file here if you want to override the default
+# path or you're using an unsupported operating system.
+# hostsPath=/etc/hosts
+
+# FetchType specifies the way Dual should retrieve the desired IP address that
+# is going to be associated with the specified hostname.
+#
+# The following values are allowed for this option:
+# 	- Resolve: gets the target IP address by resolving the provided address.
+# 	- RawFetch: gets the target IP address by connecting to the provided
+# 	  address that outputs the desired IP address in plain text.
+FetchType=Resolve
+
+# The Source value should be equal to a domain name (like foo.example.org) when
+# using the Resolve Type or equal to a web URL (like
+# https://www.example.org/api/get?entry=913804).
+Source=Nautilus.luca0N.com
+
+# The Target value is the desired local hostname.
+Target=Nautilus
diff --git a/src/com/luca0n/dual/common/ConfigSyntaxException.java b/src/com/luca0n/dual/common/ConfigSyntaxException.java
new file mode 100644
index 0000000..d542e69
--- /dev/null
+++ b/src/com/luca0n/dual/common/ConfigSyntaxException.java
@@ -0,0 +1,32 @@
+/*
+Dual: a simple manager for custom hostnames
+
+Copyright (C) 2021 luca0N!
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <https://www.gnu.org/licenses/>.
+
+Contact me by e-mail via <luca0n [at] luca0n [dot] com>.
+*/
+
+package com.luca0n.dual.common;
+
+import java.lang.Exception;
+
+public class ConfigSyntaxException extends Exception {
+	public ConfigSyntaxException(){
+		super();
+	}
+	public ConfigSyntaxException(String message){
+		super(message);
+	}
+}
diff --git a/src/com/luca0n/dual/common/Dual.java b/src/com/luca0n/dual/common/Dual.java
new file mode 100644
index 0000000..ed3c468
--- /dev/null
+++ b/src/com/luca0n/dual/common/Dual.java
@@ -0,0 +1,159 @@
+/*
+Dual: a simple manager for custom hostnames
+
+Copyright (C) 2021 luca0N!
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <https://www.gnu.org/licenses/>.
+
+Contact me by e-mail via <luca0n [at] luca0n [dot] com>.
+*/
+
+package com.luca0n.dual.common;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.FileSystems;
+import java.nio.file.Path;
+
+import com.luca0n.dual.common.ConfigSyntaxException;
+import com.luca0n.dual.common.NoSuchNamespaceException;
+import com.luca0n.dual.common.NoSuchKeyException;
+import com.luca0n.dual.common.UnsupportedOperatingSystemException;
+import com.luca0n.dual.config.Config;
+import com.luca0n.dual.config.ConfigUtil;
+
+/**
+ * @version 1.0
+ * @since 2021-03-21
+ */
+public class Dual {
+	public static final String NAME = "Dual";
+	public static final String VERSION = "1.0";
+	private static final String AUTO_GEN_COMMENT = "This entry was auto-generated by " + NAME + ".";
+	public static final int VERSION_CODE = 1;
+
+	private static final String[] SUPPORTED_OPERATING_SYSTEMS = {
+		"Linux",
+		"Windows"
+	};
+
+	public static void main(String[] args){
+		try {
+			run();
+		} catch (Exception e){
+			e.printStackTrace();
+			System.exit(1);
+		}
+	}
+	public static void run() throws ConfigSyntaxException,
+		NoSuchNamespaceException, NoSuchKeyException, IOException,
+		UnsupportedOperatingSystemException {
+		// Read configuration file
+		Config c = ConfigUtil.fromFile(ConfigUtil.DEFAULT_CONFIG);
+
+		Config.Namespace n = c.getNamespace("Dual");
+
+		if (n == null)
+			throw new NoSuchNamespaceException("Could not find required namespace Dual in the default configuration file.");
+
+		String type = n.getValue("FetchType"),
+			source = n.getValue("Source"),
+			target = n.getValue("Target"),
+			hostsPath = n.getValue("hostsPath");
+
+		// Check for null values.
+		if (source == null)
+			throw new NoSuchKeyException("Could not find required key Dual.Source in the default configuration file.");
+		else if (target == null)
+			throw new NoSuchKeyException("Could not find required key Dual.Target in the default configuration file.");
+
+		System.out.printf("%s: All tests passed.\n", NAME);
+
+		if (type == null){
+			type = "Resolve";
+			System.out.printf("%s: WARNING: no FetchType specified. Assuming Resolve FetchType...\n", NAME);
+		}
+
+		System.out.printf("%s: Using %s FetchType and %s Source.\n", NAME, type, source);
+		System.out.printf("%s: Using %s hostname.\n", NAME, target);
+
+		// Check OS.
+		String os = System.getProperty("os.name");
+		boolean supportedOs = false;
+		for (String sos : SUPPORTED_OPERATING_SYSTEMS)
+			if (os.contains(sos)){
+				supportedOs = true;
+				break;
+			}
+
+		if (!supportedOs && hostsPath == null){
+			StringBuilder msg = new StringBuilder();
+			msg.append("Unsupported operating system: ")
+				.append(os)
+				.append(". ")
+				.append("This program must be run under ");
+
+			for (int x = 0; x < SUPPORTED_OPERATING_SYSTEMS.length; x++){
+				if (x == SUPPORTED_OPERATING_SYSTEMS.length - 1)
+					msg.append(" or ")
+						.append(SUPPORTED_OPERATING_SYSTEMS[x])
+						.append(". ");
+				else if (x == 0)
+					msg.append(SUPPORTED_OPERATING_SYSTEMS[x]);
+				else
+					msg.append(", ")
+						.append(SUPPORTED_OPERATING_SYSTEMS[x]);
+			}
+
+			msg.append("If you want to override this system requirement, please provide a path to the hosts file on your operating system.");
+
+			throw new UnsupportedOperatingSystemException(msg.toString());
+		}
+
+		System.out.printf(hostsPath == null ? "%s: using %s settings.\n" : "%s: using custom settings for %s.\n", NAME, os);
+
+		// Open hosts file.
+		
+		if (hostsPath == null){
+			boolean isWindows = os.contains(SUPPORTED_OPERATING_SYSTEMS[1]);
+			hostsPath = isWindows ? "C:\\WINDOWS\\System32\\drivers\\etc\\hosts" : "/etc/hosts";
+		}
+
+		System.out.printf("%s: opening %s...\n", NAME, hostsPath);
+
+		Path path = FileSystems.getDefault().getPath(hostsPath);
+		byte[] fileBytes = Files.readAllBytes(path);
+
+		String[] lines = new String(fileBytes).split(System.lineSeparator());
+
+		for (String line : lines){
+			// Check if this line is a comment.
+			if (line.startsWith("#"))
+				// Ignore this line.
+				continue;
+			
+			String[] contents = line.split("#")[0];
+			// Check if this line was auto-generated by this program.
+			if (contents.length == 2){
+				// Check line comment.
+				if (contents[1].equals(AUTO_GEN_COMMENT)){
+					// Remove this entry if we're going to replace it.
+					
+				}
+			}
+
+
+		}
+
+	}
+}
diff --git a/src/com/luca0n/dual/common/NoSuchKeyException.java b/src/com/luca0n/dual/common/NoSuchKeyException.java
new file mode 100644
index 0000000..e0d3818
--- /dev/null
+++ b/src/com/luca0n/dual/common/NoSuchKeyException.java
@@ -0,0 +1,32 @@
+/*
+Dual: a simple manager for custom hostnames
+
+Copyright (C) 2021 luca0N!
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <https://www.gnu.org/licenses/>.
+
+Contact me by e-mail via <luca0n [at] luca0n [dot] com>.
+*/
+
+package com.luca0n.dual.common;
+
+import java.lang.Exception;
+
+public class NoSuchKeyException extends Exception {
+	public NoSuchKeyException(){
+		super();
+	}
+	public NoSuchKeyException(String message){
+		super(message);
+	}
+}
diff --git a/src/com/luca0n/dual/common/NoSuchNamespaceException.java b/src/com/luca0n/dual/common/NoSuchNamespaceException.java
new file mode 100644
index 0000000..ba1cc3b
--- /dev/null
+++ b/src/com/luca0n/dual/common/NoSuchNamespaceException.java
@@ -0,0 +1,32 @@
+/*
+Dual: a simple manager for custom hostnames
+
+Copyright (C) 2021 luca0N!
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <https://www.gnu.org/licenses/>.
+
+Contact me by e-mail via <luca0n [at] luca0n [dot] com>.
+*/
+
+package com.luca0n.dual.common;
+
+import java.lang.Exception;
+
+public class NoSuchNamespaceException extends Exception {
+	public NoSuchNamespaceException(){
+		super();
+	}
+	public NoSuchNamespaceException(String message){
+		super(message);
+	}
+}
diff --git a/src/com/luca0n/dual/common/UnsupportedOperatingSystemException.java b/src/com/luca0n/dual/common/UnsupportedOperatingSystemException.java
new file mode 100644
index 0000000..d5feb4a
--- /dev/null
+++ b/src/com/luca0n/dual/common/UnsupportedOperatingSystemException.java
@@ -0,0 +1,32 @@
+/*
+Dual: a simple manager for custom hostnames
+
+Copyright (C) 2021 luca0N!
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <https://www.gnu.org/licenses/>.
+
+Contact me by e-mail via <luca0n [at] luca0n [dot] com>.
+*/
+
+package com.luca0n.dual.common;
+
+import java.lang.Exception;
+
+public class UnsupportedOperatingSystemException extends Exception {
+	public UnsupportedOperatingSystemException(){
+		super();
+	}
+	public UnsupportedOperatingSystemException(String message){
+		super(message);
+	}
+}
diff --git a/src/com/luca0n/dual/config/Config.java b/src/com/luca0n/dual/config/Config.java
new file mode 100644
index 0000000..88cbd40
--- /dev/null
+++ b/src/com/luca0n/dual/config/Config.java
@@ -0,0 +1,64 @@
+/*
+Dual: a simple manager for custom hostnames
+
+Copyright (C) 2021 luca0N!
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <https://www.gnu.org/licenses/>.
+
+Contact me by e-mail via <luca0n [at] luca0n [dot] com>.
+*/
+
+package com.luca0n.dual.config;
+
+import java.util.List;
+import java.util.Map;
+import java.util.HashMap;
+
+/**
+ * @since 2021-03-21
+ */
+public class Config {
+	List<Namespace> namespaces;
+	protected Config(List<Namespace> namespaces){
+		this.namespaces = namespaces;
+	}
+
+	public Namespace getNamespace(String name){
+		for (Namespace n : namespaces)
+			if (n.getName().equals(name))
+				return n;
+		return null;
+	}
+
+	public static class Namespace {
+		private Map<String, String> entries;
+		private String name;
+		protected Namespace(String name){
+			this.name = name;
+			this.entries = new HashMap<>();
+		}
+		protected Namespace(String name, Map<String, String> entries){
+			this.name = name;
+			this.entries = entries;
+		}
+		protected void putEntry(String k, String v){
+			entries.put(k, v);
+		}
+		public String getValue(String key){
+			return entries.get(key);
+		}
+		public String getName(){
+			return name;
+		}
+	}
+}
diff --git a/src/com/luca0n/dual/config/ConfigUtil.java b/src/com/luca0n/dual/config/ConfigUtil.java
new file mode 100644
index 0000000..d0f0d95
--- /dev/null
+++ b/src/com/luca0n/dual/config/ConfigUtil.java
@@ -0,0 +1,87 @@
+/*
+Dual: a simple manager for custom hostnames
+
+Copyright (C) 2021 luca0N!
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <https://www.gnu.org/licenses/>.
+
+Contact me by e-mail via <luca0n [at] luca0n [dot] com>.
+*/
+
+package com.luca0n.dual.config;
+
+import java.util.List;
+import java.util.ArrayList;
+import java.util.Map;
+import java.util.HashMap;
+import java.nio.file.Path;
+import java.nio.file.FileSystems;
+import java.nio.file.Files;
+import java.io.IOException;
+
+import com.luca0n.dual.common.ConfigSyntaxException;
+import com.luca0n.dual.config.Config;
+
+/**
+ * @since @2021-03-21
+ */
+public class ConfigUtil {
+	public static final String DEFAULT_CONFIG = "gen.cfg";
+	public static Config fromFile(String filename)
+			throws IOException, ConfigSyntaxException{
+		Path path = FileSystems.getDefault().getPath("cfg", filename);
+		byte[] fileBytes = Files.readAllBytes(path);
+
+		String[] lines = new String(fileBytes).split(System.lineSeparator());
+
+		Map<String, String> v = new HashMap<>();
+		List<Config.Namespace> n = new ArrayList<>();
+		Config.Namespace currentNamespace = null;
+
+		for (String line : lines){
+			// Ignore commented lines.
+			if (line.startsWith("#"))
+				continue;
+
+			// Ignore comments.
+			String content = line.split("#")[0];
+
+			// Check if this is a namespace declaration.
+			if (content.startsWith("[")){
+				// This line must end with a "]".
+				if (!content.endsWith("]"))
+					throw new ConfigSyntaxException("Invalid namespace declaration: missing \"]\"");
+				// Append current namespace to the namespace array if it exists.
+				if (currentNamespace != null)
+					n.add(currentNamespace);
+				// Create a new namespace.
+				String nsName = content.substring(1, content.length() - 1);
+				currentNamespace = new Config.Namespace(nsName);
+			}
+
+			// Check if this is a K/V line.
+			if (content.contains("=")){
+				String[] contentSplit = content.split("=");
+				String key = contentSplit[0],
+					value = contentSplit[1];
+				currentNamespace.putEntry(key, value);
+			}
+		}
+
+		// Add the last namespace to the namespace array.
+		n.add(currentNamespace);
+
+		Config c = new Config(n);
+		return c;
+	}
+}