diff --git a/src/NATS.Server/NatsOptions.cs b/src/NATS.Server/NatsOptions.cs
new file mode 100644
index 0000000..60238c0
--- /dev/null
+++ b/src/NATS.Server/NatsOptions.cs
@@ -0,0 +1,13 @@
+namespace NATS.Server;
+
+public sealed class NatsOptions
+{
+    public string Host { get; set; } = "0.0.0.0";
+    public int Port { get; set; } = 4222;
+    public string? ServerName { get; set; }
+    public int MaxPayload { get; set; } = 1024 * 1024; // 1MB
+    public int MaxControlLine { get; set; } = 4096;
+    public int MaxConnections { get; set; } = 65536;
+    public TimeSpan PingInterval { get; set; } = TimeSpan.FromMinutes(2);
+    public int MaxPingsOut { get; set; } = 2;
+}
diff --git a/src/NATS.Server/Protocol/NatsProtocol.cs b/src/NATS.Server/Protocol/NatsProtocol.cs
new file mode 100644
index 0000000..1d126bc
--- /dev/null
+++ b/src/NATS.Server/Protocol/NatsProtocol.cs
@@ -0,0 +1,87 @@
+using System.Text.Json.Serialization;
+
+namespace NATS.Server.Protocol;
+
+public static class NatsProtocol
+{
+    public const int MaxControlLineSize = 4096;
+    public const int MaxPayloadSize = 1024 * 1024; // 1MB
+    public const int DefaultPort = 4222;
+    public const string Version = "0.1.0";
+    public const int ProtoVersion = 1;
+
+    // Pre-encoded protocol fragments
+    public static readonly byte[] CrLf = "\r\n"u8.ToArray();
+    public static readonly byte[] PingBytes = "PING\r\n"u8.ToArray();
+    public static readonly byte[] PongBytes = "PONG\r\n"u8.ToArray();
+    public static readonly byte[] OkBytes = "+OK\r\n"u8.ToArray();
+    public static readonly byte[] InfoPrefix = "INFO "u8.ToArray();
+    public static readonly byte[] MsgPrefix = "MSG "u8.ToArray();
+    public static readonly byte[] HmsgPrefix = "HMSG "u8.ToArray();
+    public static readonly byte[] ErrPrefix = "-ERR "u8.ToArray();
+}
+
+public sealed class ServerInfo
+{
+    [JsonPropertyName("server_id")]
+    public required string ServerId { get; set; }
+
+    [JsonPropertyName("server_name")]
+    public required string ServerName { get; set; }
+
+    [JsonPropertyName("version")]
+    public required string Version { get; set; }
+
+    [JsonPropertyName("proto")]
+    public int Proto { get; set; } = NatsProtocol.ProtoVersion;
+
+    [JsonPropertyName("host")]
+    public required string Host { get; set; }
+
+    [JsonPropertyName("port")]
+    public int Port { get; set; }
+
+    [JsonPropertyName("headers")]
+    public bool Headers { get; set; } = true;
+
+    [JsonPropertyName("max_payload")]
+    public int MaxPayload { get; set; } = NatsProtocol.MaxPayloadSize;
+
+    [JsonPropertyName("client_id")]
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
+    public ulong ClientId { get; set; }
+
+    [JsonPropertyName("client_ip")]
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    public string? ClientIp { get; set; }
+}
+
+public sealed class ClientOptions
+{
+    [JsonPropertyName("verbose")]
+    public bool Verbose { get; set; }
+
+    [JsonPropertyName("pedantic")]
+    public bool Pedantic { get; set; }
+
+    [JsonPropertyName("echo")]
+    public bool Echo { get; set; } = true;
+
+    [JsonPropertyName("name")]
+    public string? Name { get; set; }
+
+    [JsonPropertyName("lang")]
+    public string? Lang { get; set; }
+
+    [JsonPropertyName("version")]
+    public string? Version { get; set; }
+
+    [JsonPropertyName("protocol")]
+    public int Protocol { get; set; }
+
+    [JsonPropertyName("headers")]
+    public bool Headers { get; set; }
+
+    [JsonPropertyName("no_responders")]
+    public bool NoResponders { get; set; }
+}