Introduction & Protocol Overview

China Telecom Short Message Gateway Protocol (SMGP) is a communication protocol developed by China Netcom to implement SMS services. Its full name is Short Message Gateway Protocol. It is used between the Short Message Gateway (SMGW) and the Service Provider (SP). Communication between Short Message Gateway (SMGW) and Short Message Gateway (SMGW).

Perl is an old scripting language that is installed by default on many Linux systems. For example, in the base image of version 22.04 of Ubuntu, there is not even Python, but Perl is still installed. The popularity of Perl is evident. Perl's IO::Async module provides a concise asynchronous IO programming model.

The SMGP protocol works on a client/server model. The client (SMS application, such as mobile phone, application, etc.) first establishes a long TCP connection with the SMS Gateway (SMGW Short Message Gateway), and uses CNGP commands to interact with SMGW to send and receive SMS messages. In the CNGP protocol, the next command can be sent without waiting for a response synchronously. Implementers can implement two message transmission modes, synchronous and asynchronous, according to their own needs to meet performance requirements in different scenarios.

Timing diagram

Connection successful, send text message

Connection successful, SMS received from SMGW

Introduction to protocol frames

SMGP Header

Header contains the following fields, the size and length of which are all 4 bytes

Packet Length : The length of the entire PDU, including Header and Body.
Request ID : Used to identify the type of PDU (for example, Login, Submit, etc.).
Sequence Id : Sequence number, used to match requests and responses.

Use perl to establish connections in the SMGP protocol stack

├── Makefile.PL
├── examples
│   └── smgp_client_login_example.pl
└── lib
    └── Smgp
        ├── BoundAtomic.pm
        ├── Client.pm
        ├── Constant.pm
        └── Protocol.pm

Makefile.PL : used to generate Makefile

examples: stores sample code

smgp_client_login_example.pl: stores Smgp login example

lib/Smgp: Contains all Perl module files

BoundAtomic.pm: incremental tool class used to generate SequenceId
Client.pm: Smgp definition, responsible for communicating with Smgp services, such as establishing connections, sending text messages, etc.
Protocol.pm: stores PDU, codec, etc.

Implement sequence_id increment

sequence_id is a value from 1 to 0x7FFFFFFFF

package Smgp::BoundAtomic;

use strict;
use warnings FATAL => 'all';

sub new {
    my ($class, %args) = @_;
    my $self = {
        min     => $args{min},
        max     => $args{max},
        value   => $args{min},
    };
    bless $self, $class;
    return $self;
}

sub increment {
    my ($self) = @_;
    if ($self->{value} >= $self->{max}) {
        $self->{value} = $self->{min};
    } else {
        $self->{value}++;
    }
    return $self->{value};
}

sub get {
    my ($self) = @_;
    return $self->{value};
}

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Define SMGP PDU and encoding and decoding functions in Perl

package Smgp::Protocol;

use strict;
use warnings FATAL => 'all';

use Smgp::Constant;

sub new_login {
    my ($class, %args) = @_;
    my $self = {
        clientId            => $args{clientId},
        authenticatorClient => $args{authenticatorClient},
        loginMode           => $args{loginMode},
        timeStamp           => $args{timeStamp},
        version             => $args{version},
    };
    return bless $self, $class;
}

sub encode_login {
    my ($self) = @_;
    return pack("A8A16CNC", @{$self}{qw(clientId authenticatorClient loginMode timeStamp version)});
}

sub decode_login_resp {
    my ($class, $buffer) = @_;
    my ($status, $authenticatorServer, $version) = unpack("N4A16C", $buffer);
    return bless {
        status              => $status,
        authenticatorServer => $authenticatorServer,
        version             => $version,
    }, $class;
}

sub new_header {
    my ($class, %args) = @_;
    my $self = {
        total_length   => $args{total_length},
        request_id     => $args{request_id},
        command_status => $args{command_status},
        sequence_id    => $args{sequence_id},
    };
    return bless $self, $class;
}

sub encode_header {
    my ($self, $total_length) = @_;
    return pack("N3", $total_length, @{$self}{qw(request_id sequence_id)});
}

sub new_pdu {
    my ($class, %args) = @_;
    my $self = {
        header => $args{header},
        body   => $args{body},
    };
    return bless $self, $class;
}

sub encode_login_pdu {
    my ($self) = @_;
    my $encoded_body = $self->{body}->encode_login();
    return $self->{header}->encode_header(length($encoded_body) + 12) . $encoded_body;
}

sub decode_pdu {
    my ($class, $buffer) = @_;
    my ($request_id, $sequence_id) = unpack("N2", substr($buffer, 0, 8));
    my $body_buffer = substr($buffer, 8);

    my $header = $class->new_header(
        total_length   => 0,
        request_id     => $request_id,
        sequence_id    => $sequence_id,
    );

    my $body;
    if ($request_id == Smgp::Constant::LOGIN_RESP_ID) {
        $body = $class->decode_login_resp($body_buffer);
    } else {
        die "Unsupported request_id: $request_id";
    }

    return $class->new_pdu(
        header => $header,
        body   => $body,
    );
}

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constant.pm stores related requestId

package Smgp::Constant;

use strict;
use warnings FATAL => 'all';

use constant {
    LOGIN_ID               => 0x00000001,
    LOGIN_RESP_ID          => 0x80000001,
    SUBMIT_ID              => 0x00000002,
    SUBMIT_RESP_ID         => 0x80000002,
    DELIVER_ID             => 0x00000003,
    DELIVER_RESP_ID        => 0x80000003,
    ACTIVE_TEST_ID         => 0x00000004,
    ACTIVE_TEST_RESP_ID    => 0x80000004,
    FORWARD_ID             => 0x00000005,
    FORWARD_RESP_ID        => 0x80000005,
    EXIT_ID                => 0x00000006,
    EXIT_RESP_ID           => 0x80000006,
    QUERY_ID               => 0x00000007,
    QUERY_RESP_ID          => 0x80000007,
    MT_ROUTE_UPDATE_ID     => 0x00000008,
    MT_ROUTE_UPDATE_RESP_ID => 0x80000008,
};

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Implement client and login methods

package Smgp::Client;
use strict;
use warnings FATAL => 'all';
use IO::Socket::INET;

use Smgp::Protocol;
use Smgp::Constant;

sub new {
    my ($class, %args) = @_;
    my $self = {
        host => $args{host} // 'localhost',
        port => $args{port} // 9000,
        socket => undef,
        sequence_id => 1,
    };
    bless $self, $class;
    return $self;
}

sub connect {
    my ($self) = @_;
    $self->{socket} = IO::Socket::INET->new(
        PeerHost => $self->{host},
        PeerPort => $self->{port},
        Proto => 'tcp',
    ) or die "Cannot connect to $self->{host}:$self->{port} $!";
}

sub login {
    my ($self, $body) = @_;
    my $header = Smgp::Protocol->new_header(
        request_id     => Smgp::Constant::LOGIN_ID,
        sequence_id    => 1,
    );

    my $pdu = Smgp::Protocol->new_pdu(
        header => $header,
        body   => $body,
    );

    $self->{socket}->send($pdu->encode_login_pdu());

    $self->{socket}->recv(my $response_length_bytes, 4);

    my $total_length = unpack("N", $response_length_bytes);
    my $remain_length = $total_length - 4;
    $self->{socket}->recv(my $response_data, $remain_length);

    return Smgp::Protocol->decode_pdu($response_data)->{body};
}

sub disconnect {
    my ($self) = @_;
    close($self->{socket}) if $self->{socket};
}

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Run example to verify the connection is successful

package smgp_client_login_example;

use strict;
use warnings FATAL => 'all';

use Smgp::Client;
use Smgp::Protocol;
use Smgp::Constant;

sub main {
    my $client = Smgp::Client->new(
        host => 'localhost',
        port => 9000,
    );

    $client->connect();

    my $login = Smgp::Protocol->new_login(
        clientId            => '12345678',
        authenticatorClient => '1234567890123456',
        loginMode           => 1,
        timeStamp           => time(),
        version             => 0,
    );

    my $response = $client->login($login);

    if ($response->{status} == 0) {
        print "Login successful!\n";
    }
    else {
        print "Login failed! Status: ", (defined $response->{status} ? $response->{status} : 'undefined'), "\n";
    }

    $client->disconnect();
}

main() unless caller;

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Related open source projects

netty-codec-sms stores netty codecs for various SMS protocols (such as cmpp, sgip, smpp)
sms-client-java stores Java clients of various SMS protocols
sms-server-java stores Java servers for various SMS protocols
cmpp-python python implementation of cmpp protocol
python implementation of cngp-zig cmpp protocol
smgp-perl perl implementation of smgp protocol
smpp-rust rust implementation of smpp protocol

Summarize

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Teach you how to implement Smgp protocol using Perl