diff --git a/lib/defs.d.ts b/lib/defs.d.ts
new file mode 100644
index 0000000..a55570e
--- /dev/null
+++ b/lib/defs.d.ts
@@ -0,0 +1,869 @@
+declare module 'smpp' {
+  namespace defs {
+    type AvailableEncodings = 'ASCII' | 'LATIN1' | 'UCS2';
+    type AvailableGSMCoder = 'GSM' | 'GSM_TR' | 'GSM_ES' | 'GSM_PT';
+    type AvailableTypes =
+      | 'int8'
+      | 'int16'
+      | 'int32'
+      | 'string'
+      | 'cstring'
+      | 'buffer'
+      | 'dest_address_array'
+      | 'unsuccess_sme_array';
+
+    type Gsmcoder = {
+      chars: string;
+      extCharsEnc?: string;
+      escCharsEnc?: string;
+      extCharsDec?: string;
+      escCharsDec?: string;
+      charRegex: string;
+      charListEnc: object;
+      extCharListEnc: object;
+      charListDec: object;
+      extCharListDec: object;
+    };
+
+    type Type = {
+      read: <T>(buffer: Buffer, offset: number) => T;
+      write: <T>(value: T, buffer: Buffer, offset: number) => void;
+      size: <T>(value?: T) => number;
+      default: any;
+    };
+
+    type TypeTlv = {
+      read: (buffer: Buffer, offset: number, length: number) => string;
+      write: <T>(value: T, buffer: Buffer, offset: number) => void;
+      size: <T>(value: T) => number;
+      default: any;
+    };
+
+    type Encoder = {
+      match(value: string): boolean;
+      encode(value: string): Buffer;
+      decode(value: Buffer): string;
+    };
+
+    type Filter<EV, ER, DV, DR> = {
+      encode(value: EV): ER;
+      decode(value: DV, skipUdh?: boolean): DR;
+    };
+
+    type Encodings = {
+      [K in AvailableEncodings]: Encoder;
+    };
+
+    type BufferReturn = {
+      format: number;
+      data: string | Buffer;
+    };
+
+    type MessageEncode = {
+      message: string;
+      udh?: Buffer;
+    };
+
+    type MessageDecode = {
+      message: string | Buffer;
+      udh?: Buffer[];
+    };
+
+    type BroadcastContent = {
+      network: number;
+      content_type: number;
+    };
+
+    type BroadcastFrequency = {
+      unit: number;
+      interval: number;
+    };
+
+    type CallbackNum = {
+      digit_mode: number;
+      ton: number;
+      npi: number;
+      number: string;
+    };
+
+    type CallbackNumAtaEncode = {
+      encoding: number;
+      display: string | Buffer;
+    };
+
+    type CallbackNumAtaDencode = {
+      encoding: number;
+      display: Buffer;
+    };
+
+    type Filters = {
+      time: Filter<
+        string | Date | undefined | null,
+        string | undefined | null,
+        string | undefined | null,
+        Date | string | undefined | null
+      >;
+      message: Filter<
+        Buffer | string | Message,
+        Buffer | string,
+        Buffer,
+        MessageDecode | Buffer
+      >;
+      billing_identification: Filter<
+        Buffer | BufferReturn,
+        Buffer,
+        Buffer,
+        BufferReturn | Buffer
+      >;
+      broadcast_area_identifier: Filter<
+        Buffer | string | BufferReturn,
+        Buffer,
+        Buffer,
+        BufferReturn | Buffer
+      >;
+      broadcast_content_type: Filter<
+        Buffer | BroadcastContent,
+        Buffer,
+        Buffer,
+        BroadcastContent | Buffer
+      >;
+      broadcast_frequency_interval: Filter<
+        Buffer | BroadcastFrequency,
+        Buffer,
+        Buffer,
+        BroadcastFrequency | Buffer
+      >;
+      callback_num: Filter<
+        Buffer | Partial<CallbackNum>,
+        Buffer,
+        Buffer,
+        CallbackNum | Buffer
+      >;
+      callback_num_atag: Filter<
+        Buffer | CallbackNumAtaEncode,
+        Buffer,
+        Buffer,
+        CallbackNumAtaDencode | Buffer
+      >;
+    };
+
+    type GsmCoders = {
+      [K in AvailableGSMCoder]: Gsmcoder;
+    };
+
+    type consts = {
+      REGISTERED_DELIVERY: {
+        FINAL: number;
+        FAILURE: number;
+        SUCCESS: number;
+        DELIVERY_ACKNOWLEDGEMENT: number;
+        USER_ACKNOWLEDGEMENT: number;
+        INTERMEDIATE: number;
+      };
+      ESM_CLASS: {
+        DATAGRAM: number;
+        FORWARD: number;
+        STORE_FORWARD: number;
+        MC_DELIVERY_RECEIPT: number;
+        DELIVERY_ACKNOWLEDGEMENT: number;
+        USER_ACKNOWLEDGEMENT: number;
+        CONVERSATION_ABORT: number;
+        INTERMEDIATE_DELIVERY: number;
+        UDH_INDICATOR: number;
+        KANNEL_UDH_INDICATOR: number;
+        SET_REPLY_PATH: number;
+      };
+      MESSAGE_STATE: {
+        SCHEDULED: number;
+        ENROUTE: number;
+        DELIVERED: number;
+        EXPIRED: number;
+        DELETED: number;
+        UNDELIVERABLE: number;
+        ACCEPTED: number;
+        UNKNOWN: number;
+        REJECTED: number;
+        SKIPPED: number;
+      };
+      TON: {
+        UNKNOWN: number;
+        INTERNATIONAL: number;
+        NATIONAL: number;
+        NETWORK_SPECIFIC: number;
+        SUBSCRIBER_NUMBER: number;
+        ALPHANUMERIC: number;
+        ABBREVIATED: number;
+      };
+      NPI: {
+        UNKNOWN: number;
+        ISDN: number;
+        DATA: number;
+        TELEX: number;
+        LAND_MOBILE: number;
+        NATIONAL: number;
+        PRIVATE: number;
+        ERMES: number;
+        INTERNET: number;
+        IP: number;
+        WAP: number;
+      };
+      ENCODING: {
+        SMSC_DEFAULT: number;
+        ASCII: number;
+        GSM_TR: number;
+        GSM_ES: number;
+        GSM_PT: number;
+        IA5: number;
+        LATIN1: number;
+        ISO_8859_1: number;
+        BINARY: number;
+        JIS: number;
+        X_0208_1990: number;
+        CYRILLIC: number;
+        ISO_8859_5: number;
+        HEBREW: number;
+        ISO_8859_8: number;
+        UCS2: number;
+        PICTOGRAM: number;
+        ISO_2022_JP: number;
+        EXTENDED_KANJI_JIS: number;
+        X_0212_1990: number;
+        KS_C_5601: number;
+      };
+      NETWORK: {
+        GENERIC: number;
+        GSM: number;
+        TDMA: number;
+        CDMA: number;
+      };
+      BROADCAST_AREA_FORMAT: {
+        NAME: number;
+        ALIAS: number;
+        ELLIPSOID_ARC: number;
+        POLYGON: number;
+      };
+      BROADCAST_FREQUENCY_INTERVAL: {
+        MAX_POSSIBLE: number;
+        SECONDS: number;
+        MINUTES: number;
+        HOURS: number;
+        DAYS: number;
+        WEEKS: number;
+        MONTHS: number;
+        YEARS: number;
+      };
+    };
+
+    type Types = {
+      [K in AvailableTypes]: Type;
+    };
+
+    type TypesTlv = {
+      int8: Types['int8'];
+      int16: Types['int16'];
+      int32: Types['int32'];
+      cstring: Types['cstring'];
+      string: TypesTlv;
+      buffer: TypesTlv;
+    };
+
+    type Commands = {
+      alert_notification: {
+        id: number;
+        params: {
+          source_addr_ton: { type: Types['int8'] };
+          source_addr_npi: { type: Types['int8'] };
+          source_addr: { type: Types['cstring'] };
+          esme_addr_ton: { type: Types['int8'] };
+          esme_addr_npi: { type: Types['int8'] };
+          esme_addr: { type: Types['cstring'] };
+        };
+      };
+      bind_receiver: {
+        id: number;
+        params: {
+          system_id: { type: Types['cstring'] };
+          password: { type: Types['cstring'] };
+          system_type: { type: Types['cstring'] };
+          interface_version: { type: Types['int8']; default: number };
+          addr_ton: { type: Types['int8'] };
+          addr_npi: { type: Types['int8'] };
+          address_range: { type: Types['cstring'] };
+        };
+      };
+      bind_receiver_resp: {
+        id: number;
+        params: {
+          system_id: { type: Types['cstring'] };
+        };
+      };
+      bind_transmitter: {
+        id: number;
+        params: {
+          system_id: { type: Types['cstring'] };
+          password: { type: Types['cstring'] };
+          system_type: { type: Types['cstring'] };
+          interface_version: { type: Types['int8']; default: number };
+          addr_ton: { type: Types['int8'] };
+          addr_npi: { type: Types['int8'] };
+          address_range: { type: Types['cstring'] };
+        };
+      };
+      bind_transmitter_resp: {
+        id: number;
+        params: {
+          system_id: { type: Types['cstring'] };
+        };
+      };
+      bind_transceiver: {
+        id: number;
+        params: {
+          system_id: { type: Types['cstring'] };
+          password: { type: Types['cstring'] };
+          system_type: { type: Types['cstring'] };
+          interface_version: { type: Types['int8']; default: number };
+          addr_ton: { type: Types['int8'] };
+          addr_npi: { type: Types['int8'] };
+          address_range: { type: Types['cstring'] };
+        };
+      };
+      bind_transceiver_resp: {
+        id: number;
+        params: {
+          system_id: { type: Types['cstring'] };
+        };
+      };
+      broadcast_sm: {
+        id: number;
+        params: {
+          service_type: { type: Types['cstring'] };
+          source_addr_ton: { type: Types['int8'] };
+          source_addr_npi: { type: Types['int8'] };
+          source_addr: { type: Types['cstring'] };
+          message_id: { type: Types['cstring'] };
+          priority_flag: { type: Types['int8'] };
+          schedule_delivery_time: {
+            type: Types['cstring'];
+            filter: Filters['time'];
+          };
+          validity_period: { type: Types['cstring']; filter: Filters['time'] };
+          replace_if_present_flag: { type: Types['int8'] };
+          data_coding: { type: Types['int8']; default: null };
+          sm_default_msg_id: { type: Types['int8'] };
+        };
+      };
+      broadcast_sm_resp: {
+        id: number;
+        params: {
+          message_id: { type: Types['cstring'] };
+        };
+        tlvMap: {
+          broadcast_area_identifier: 'failed_broadcast_area_identifier';
+        };
+      };
+      cancel_broadcast_sm: {
+        id: number;
+        params: {
+          service_type: { type: Types['cstring'] };
+          message_id: { type: Types['cstring'] };
+          source_addr_ton: { type: Types['int8'] };
+          source_addr_npi: { type: Types['int8'] };
+          source_addr: { type: Types['cstring'] };
+        };
+      };
+      cancel_broadcast_sm_resp: {
+        id: number;
+      };
+      cancel_sm: {
+        id: number;
+        params: {
+          service_type: { type: Types['cstring'] };
+          message_id: { type: Types['cstring'] };
+          source_addr_ton: { type: Types['int8'] };
+          source_addr_npi: { type: Types['int8'] };
+          source_addr: { type: Types['cstring'] };
+          dest_addr_ton: { type: Types['int8'] };
+          dest_addr_npi: { type: Types['int8'] };
+          destination_addr: { type: Types['cstring'] };
+        };
+      };
+      cancel_sm_resp: {
+        id: number;
+      };
+      data_sm: {
+        id: number;
+        params: {
+          service_type: { type: Types['cstring'] };
+          source_addr_ton: { type: Types['int8'] };
+          source_addr_npi: { type: Types['int8'] };
+          source_addr: { type: Types['cstring'] };
+          dest_addr_ton: { type: Types['int8'] };
+          dest_addr_npi: { type: Types['int8'] };
+          destination_addr: { type: Types['cstring'] };
+          esm_class: { type: Types['int8'] };
+          registered_delivery: { type: Types['int8'] };
+          data_coding: { type: Types['int8']; default: null };
+        };
+      };
+      data_sm_resp: {
+        id: number;
+        params: {
+          message_id: { type: Types['cstring'] };
+        };
+      };
+      deliver_sm: {
+        id: number;
+        params: {
+          service_type: { type: Types['cstring'] };
+          source_addr_ton: { type: Types['int8'] };
+          source_addr_npi: { type: Types['int8'] };
+          source_addr: { type: Types['cstring'] };
+          dest_addr_ton: { type: Types['int8'] };
+          dest_addr_npi: { type: Types['int8'] };
+          destination_addr: { type: Types['cstring'] };
+          esm_class: { type: Types['int8'] };
+          protocol_id: { type: Types['int8'] };
+          priority_flag: { type: Types['int8'] };
+          schedule_delivery_time: {
+            type: Types['cstring'];
+            filter: Filters['time'];
+          };
+          validity_period: { type: Types['cstring']; filter: Filters['time'] };
+          registered_delivery: { type: Types['int8'] };
+          replace_if_present_flag: { type: Types['int8'] };
+          data_coding: { type: Types['int8']; default: null };
+          sm_default_msg_id: { type: Types['int8'] };
+          short_message: { type: Types['buffer']; filter: Filters['message'] };
+        };
+      };
+      deliver_sm_resp: {
+        id: number;
+        params: {
+          message_id: { type: Types['cstring'] };
+        };
+      };
+      enquire_link: {
+        id: number;
+      };
+      enquire_link_resp: {
+        id: number;
+      };
+      generic_nack: {
+        id: number;
+      };
+      outbind: {
+        id: number;
+        params: {
+          system_id: { type: Types['cstring'] };
+          password: { type: Types['cstring'] };
+        };
+      };
+      query_broadcast_sm: {
+        id: number;
+        params: {
+          message_id: { type: Types['cstring'] };
+          source_addr_ton: { type: Types['int8'] };
+          source_addr_npi: { type: Types['int8'] };
+          source_addr: { type: Types['cstring'] };
+        };
+      };
+      query_broadcast_sm_resp: {
+        id: number;
+        params: {
+          message_id: { type: Types['cstring'] };
+        };
+      };
+      query_sm: {
+        id: number;
+        params: {
+          message_id: { type: Types['cstring'] };
+          source_addr_ton: { type: Types['int8'] };
+          source_addr_npi: { type: Types['int8'] };
+          source_addr: { type: Types['cstring'] };
+        };
+      };
+      query_sm_resp: {
+        id: number;
+        params: {
+          message_id: { type: Types['cstring'] };
+          final_date: { type: Types['cstring']; filter: Filters['time'] };
+          message_state: { type: Types['int8'] };
+          error_code: { type: Types['int8'] };
+        };
+      };
+      replace_sm: {
+        id: number;
+        params: {
+          message_id: { type: Types['cstring'] };
+          source_addr_ton: { type: Types['int8'] };
+          source_addr_npi: { type: Types['int8'] };
+          source_addr: { type: Types['cstring'] };
+          schedule_delivery_time: {
+            type: Types['cstring'];
+            filter: Filters['time'];
+          };
+          validity_period: { type: Types['cstring']; filter: Filters['time'] };
+          registered_delivery: { type: Types['int8'] };
+          sm_default_msg_id: { type: Types['int8'] };
+          short_message: { type: Types['buffer']; filter: Filters['message'] };
+        };
+      };
+      replace_sm_resp: {
+        id: number;
+      };
+      submit_multi: {
+        id: number;
+        params: {
+          service_type: { type: Types['cstring'] };
+          source_addr_ton: { type: Types['int8'] };
+          source_addr_npi: { type: Types['int8'] };
+          source_addr: { type: Types['cstring'] };
+          dest_address: { type: Types['dest_address_array'] };
+          esm_class: { type: Types['int8'] };
+          protocol_id: { type: Types['int8'] };
+          priority_flag: { type: Types['int8'] };
+          schedule_delivery_time: {
+            type: Types['cstring'];
+            filter: Filters['time'];
+          };
+          validity_period: { type: Types['cstring']; filter: Filters['time'] };
+          registered_delivery: { type: Types['int8'] };
+          replace_if_present_flag: { type: Types['int8'] };
+          data_coding: { type: Types['int8']; default: null };
+          sm_default_msg_id: { type: Types['int8'] };
+          short_message: { type: Types['buffer']; filter: Filters['message'] };
+        };
+      };
+      submit_multi_resp: {
+        id: number;
+        params: {
+          message_id: { type: Types['cstring'] };
+          unsuccess_sme: { type: Types['unsuccess_sme_array'] };
+        };
+      };
+      submit_sm: {
+        id: number;
+        params: {
+          service_type: { type: Types['cstring'] };
+          source_addr_ton: { type: Types['int8'] };
+          source_addr_npi: { type: Types['int8'] };
+          source_addr: { type: Types['cstring'] };
+          dest_addr_ton: { type: Types['int8'] };
+          dest_addr_npi: { type: Types['int8'] };
+          destination_addr: { type: Types['cstring'] };
+          esm_class: { type: Types['int8'] };
+          protocol_id: { type: Types['int8'] };
+          priority_flag: { type: Types['int8'] };
+          schedule_delivery_time: {
+            type: Types['cstring'];
+            filter: Filters['time'];
+          };
+          validity_period: { type: Types['cstring']; filter: Filters['time'] };
+          registered_delivery: { type: Types['int8'] };
+          replace_if_present_flag: { type: Types['int8'] };
+          data_coding: { type: Types['int8']; default: null };
+          sm_default_msg_id: { type: Types['int8'] };
+          short_message: { type: Types['buffer']; filter: Filters['message'] };
+        };
+      };
+      submit_sm_resp: {
+        id: number;
+        params: {
+          message_id: { type: Types['cstring'] };
+        };
+      };
+      unbind: {
+        id: number;
+      };
+      unbind_resp: {
+        id: number;
+      };
+    };
+
+    type CommandsById = number;
+
+    type Tlvs = {
+      dest_addr_subunit: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      dest_network_type: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      dest_bearer_type: {
+        id: number;
+        type: TypesTlv['int16'];
+      };
+      dest_telematics_id: {
+        id: number;
+        type: TypesTlv['int16'];
+      };
+      source_addr_subunit: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      source_network_type: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      source_bearer_type: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      source_telematics_id: {
+        id: number;
+        type: TypesTlv['int16'];
+      };
+      qos_time_to_live: {
+        id: number;
+        type: TypesTlv['int32'];
+      };
+      payload_type: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      additional_status_info_text: {
+        id: number;
+        type: TypesTlv['cstring'];
+      };
+      receipted_message_id: {
+        id: number;
+        type: TypesTlv['cstring'];
+      };
+      ms_msg_wait_facilities: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      privacy_indicator: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      source_subaddress: {
+        id: number;
+        type: TypesTlv['buffer'];
+      };
+      dest_subaddress: {
+        id: number;
+        type: TypesTlv['buffer'];
+      };
+      user_message_reference: {
+        id: number;
+        type: TypesTlv['int16'];
+      };
+      user_response_code: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      source_port: {
+        id: number;
+        type: TypesTlv['int16'];
+      };
+      dest_port: {
+        id: number;
+        type: TypesTlv['int16'];
+      };
+      sar_msg_ref_num: {
+        id: number;
+        type: TypesTlv['int16'];
+      };
+      language_indicator: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      sar_total_segments: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      sar_segment_seqnum: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      sc_interface_version: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      callback_num_pres_ind: {
+        id: number;
+        type: TypesTlv['int8'];
+        multiple: true;
+      };
+      callback_num_atag: {
+        id: number;
+        type: TypesTlv['buffer'];
+        filter: Filters['callback_num_atag'];
+        multiple: true;
+      };
+      number_of_messages: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      callback_num: {
+        id: number;
+        type: TypesTlv['buffer'];
+        filter: Filters['callback_num'];
+        multiple: true;
+      };
+      dpf_result: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      set_dpf: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      ms_availability_status: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      network_error_code: {
+        id: number;
+        type: TypesTlv['buffer'];
+      };
+      message_payload: {
+        id: number;
+        type: TypesTlv['buffer'];
+        filter: Filters['message'];
+      };
+      delivery_failure_reason: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      more_messages_to_send: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      message_state: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      congestion_state: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      ussd_service_op: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      broadcast_channel_indicator: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      broadcast_content_type: {
+        id: number;
+        type: TypesTlv['buffer'];
+        filter: Filters['broadcast_content_type'];
+      };
+      broadcast_content_type_info: {
+        id: number;
+        type: TypesTlv['string'];
+      };
+      broadcast_message_class: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      broadcast_rep_num: {
+        id: number;
+        type: TypesTlv['int16'];
+      };
+      broadcast_frequency_interval: {
+        id: number;
+        type: TypesTlv['buffer'];
+        filter: Filters['broadcast_frequency_interval'];
+      };
+      broadcast_area_identifier: {
+        id: number;
+        type: TypesTlv['buffer'];
+        filter: Filters['broadcast_area_identifier'];
+        multiple: true;
+      };
+      broadcast_error_status: {
+        id: number;
+        type: TypesTlv['int32'];
+        multiple: true;
+      };
+      broadcast_area_success: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      broadcast_end_time: {
+        id: number;
+        type: TypesTlv['string'];
+        filter: Filters['time'];
+      };
+      broadcast_service_group: {
+        id: number;
+        type: TypesTlv['string'];
+      };
+      billing_identification: {
+        id: number;
+        type: TypesTlv['buffer'];
+        filter: Filters['billing_identification'];
+      };
+      source_network_id: {
+        id: number;
+        type: TypesTlv['cstring'];
+      };
+      dest_network_id: {
+        id: number;
+        type: TypesTlv['cstring'];
+      };
+      source_node_id: {
+        id: number;
+        type: TypesTlv['string'];
+      };
+      dest_node_id: {
+        id: number;
+        type: TypesTlv['string'];
+      };
+      dest_addr_np_resolution: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      dest_addr_np_information: {
+        id: number;
+        type: TypesTlv['string'];
+      };
+      dest_addr_np_country: {
+        id: number;
+        type: TypesTlv['int32'];
+      };
+      display_time: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      sms_signal: {
+        id: number;
+        type: TypesTlv['int16'];
+      };
+      ms_validity: {
+        id: number;
+        type: TypesTlv['buffer'];
+      };
+      alert_on_message_delivery: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      its_reply_type: {
+        id: number;
+        type: TypesTlv['int8'];
+      };
+      its_session_info: {
+        id: number;
+        type: TypesTlv['buffer'];
+      };
+    };
+
+    type TlvsById = number;
+
+    export const encodings: Encodings;
+    export const filters: Filters;
+    export const gsmCoder: GsmCoders;
+    export const consts: consts;
+    export const commands: Commands;
+    export const commandsById: CommandsById;
+    export const types: Types;
+    export const tlvs: Tlvs;
+    export const tlvsById: TlvsById;
+  }
+}
diff --git a/lib/pdu.d.ts b/lib/pdu.d.ts
new file mode 100644
index 0000000..1c8e3d0
--- /dev/null
+++ b/lib/pdu.d.ts
@@ -0,0 +1,36 @@
+import { Socket } from 'net';
+import { defs } from 'smpp';
+
+declare module 'smpp' {
+  namespace PDU {
+    type PduBaseParams = {
+      command_length: number;
+      command_id: number;
+      command_status: number;
+      sequence_number: number;
+    };
+
+    export declare class PDU {
+      constructor(
+        command: keyof defs.Commands | Buffer,
+        options?: Record<string, any>,
+      );
+
+      command: string;
+      command_length: number;
+      command_id: number;
+      command_status: number;
+      sequence_number: number;
+
+      static commandLength(stream: Socket): number | boolean;
+      static fromStream(stream: Socket, command_length: number): PDU | boolean;
+      static fromBuffer(buffer: Buffer): PDU | boolean;
+
+      isResponse(): boolean;
+      response(options?: Options): PDU;
+      fromBuffer(buffer: Buffer): void;
+      toBuffer(): Buffer;
+    }
+  }
+  export = PDU;
+}
diff --git a/lib/smpp.d.ts b/lib/smpp.d.ts
new file mode 100644
index 0000000..85ffa41
--- /dev/null
+++ b/lib/smpp.d.ts
@@ -0,0 +1,121 @@
+import { EventEmitter } from 'events';
+import { Socket } from 'net';
+import { TLSSocket } from 'tls';
+import { defs, PDU } from 'smpp';
+import * as net from 'net';
+
+declare module 'smpp' {
+  type debugListener = (type: string, msg: string, payload: any) => void;
+
+  interface sessionOptions {
+    socket: Socket | TLSSocket;
+    tls: boolean;
+    connectTimeout: number;
+    url: string;
+    auto_enquire_link_period: number;
+    debug: boolean;
+    debugListener: debugListener;
+  }
+
+  interface serverOptions {
+    isProxiedServer: boolean;
+    key: string;
+    cert: string;
+    tls: boolean;
+    debug: boolean;
+    debugListener: debugListener;
+  }
+
+  type SessionPduEvent = keyof defs.Commands;
+  type SessionPduParams<E extends SessionPduEvent> = PDU &
+    defs.Commands[E]['params'];
+
+  type PDUMethods = {
+    [C in keyof defs.Commands]: (
+      params: Partial<{ [P in keyof defs.Commands[C]['params']]: any }>,
+      callback?: (pdu: PDU) => void,
+    ) => void;
+  };
+
+  interface Session extends PDUMethods {}
+  export declare class Session extends EventEmitter {
+    options: Partial<sessionOptions>;
+    sequence: number;
+    paused: boolean;
+    closed: boolean;
+    remoteAddress: string | null;
+    remotePort: string | null;
+    proxyProtocolProxy: string | null;
+
+    on<E extends SessionPduEvent>(
+      event: E,
+      pdu: (pdu?: SessionPduParams<E> | null) => void,
+    );
+    on(event: 'close', pdu: () => void);
+    on(event: 'error', pdu: (pdu?: unknown) => void);
+    on(event: 'unknown', pdu: (pdu?: unknown) => void);
+    on(
+      event: 'debug',
+      pdu: (type: string, message: string, payload: string) => void,
+    );
+
+    connect(): void;
+    pause(): void;
+    resume(): void;
+    close: (callback?: () => void) => void;
+    destroy: (callback?: () => void) => void;
+    send(
+      pdu: PDU,
+      responseCallback?: (callback: PDU) => void,
+      sendCallback?: (callback: any) => void,
+      failureCallback?: (callback: Error) => void,
+    ): boolean;
+  }
+
+  export declare class Server extends net.Server {
+    constructor(options: serverOptions, listener: (session: Session) => void);
+
+    options: Partial<serverOptions>;
+    isProxiedServer: boolean;
+    tls: boolean;
+    sessions: Session[];
+  }
+
+  export declare function SecureServer(
+    options: Partial<serverOptions>,
+    listener?: (session: Session) => void,
+  ): void;
+
+  export declare function ProxyServer(
+    options: Partial<serverOptions>,
+    listener?: (session: Session) => void,
+  ): void;
+
+  export declare function ProxySecureServer(
+    options: Partial<serverOptions>,
+    listener?: (session: Session) => void,
+  ): void;
+
+  export declare function createServer(
+    options: Partial<serverOptions>,
+    listener?: (session: Session) => void,
+  ): net.Server;
+
+  export declare function connect(
+    options: Partial<sessionOptions>,
+    listener?: (session: Session) => void,
+  ): Session;
+
+  export declare function addCommand(
+    command: keyof defs.Commands,
+    options: Record<string, any>,
+  ): void;
+
+  export declare function addTlv(
+    tag: keyof defs.Tlvs,
+    options: {
+      id: number;
+      type: defs.Type;
+    },
+  );
+}