协议概述

SMPP(Short Message Peer-to-Peer)协议起源于90年代，最初由Aldiscon公司开发，后来由SMPP开发者论坛维护和推广。SMPP常用于在SMSC（Short Message Service Center，短信中心）和短信应用之间传输短消息，支持高效的短信息发送、接收和查询功能，是电信运营商和短信服务提供商之间互通短信的主要协议之一。

SMPP协议基于客户端/服务端模型工作。由客户端（短信应用，如手机，应用程序等）先和SMSC建立起TCP长连接，并使用SMPP命令与SMSC进行交互，实现短信的发送和接收。在SMPP协议中，无需同步等待响应就可以发送下一个指令，实现者可以根据自己的需要，实现同步、异步两种消息传输模式，满足不同场景下的性能要求。

时序图

绑定transmitter模式，发送短信并查询短信发送成功

绑定receiver模式，从SMSC接收到短信

协议帧介绍

在SMPP协议中，每个PDU都包含两个部分：SMPP Header和SMPP Body。

SMPP Header

Header包含以下字段，大小长度都是4字节

• Command Length：整个PDU的长度，包括Header和Body。
• Command ID：用于标识PDU的类型（例如，BindReceiver、QuerySM等）。
• Command Status：响应状态码，表示处理的结果。
• Sequence Number：序列号，用来匹配请求和响应。

用Rust实现SMPP协议栈里的BindTransmitter

本文的代码均已上传到smpp-rust

选用Tokio作为基础的异步运行时环境，tokio有非常强大的异步IO支持，也是rust库的事实标准。

代码结构组织如下:

├── lib.rs
├── const.rs
├── protocol.rs
├── smpp_client.rs
└── smpp_server.rs

• lib.rs Rust项目的入口点
• const.rs 包含常量定义，如commandId、状态码等
• protocol.rs 包含PDU定义，编解码处理等
• smpp_client.rs 实现smpp客户端逻辑
• smpp_server.rs 实现

利用rust原子类实现sequence_number

sequence_number是从1到0x7FFFFFFF的值，利用Rust的AtomicI32来生成这个值。

use std::sync::atomic::{AtomicI32, Ordering};
use std::num::TryFromIntError;

struct BoundAtomicInt {
    min: i32,
    max: i32,
    integer: AtomicI32,
}

impl BoundAtomicInt {
    pub fn new(min: i32, max: i32) -> Self {
        assert!(min <= max, "min must be less than or equal to max");
        Self {
            min,
            max,
            integer: AtomicI32::new(min),
        }
    }

    pub fn next_val(&self) -> Result<i32, TryFromIntError> {
        let next = self.integer.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |x| {
            Some(if x >= self.max { self.min } else { x + 1 })
        })?;
        Ok(next)
    }
}

在Rust中定义SMPP PDU

pub struct SmppPdu {
    pub header: SmppHeader,
    pub body: SmppBody,
}

pub struct SmppHeader {
    pub command_length: i32,
    pub command_id: i32,
    pub command_status: i32,
    pub sequence_number: i32,
}

pub enum SmppBody {
    BindReceiver(BindReceiver),
    BindReceiverResp(BindReceiverResp),
    BindTransmitter(BindTransmitter),
    BindTransmitterResp(BindTransmitterResp),
    QuerySm(QuerySm),
    QuerySmResp(QuerySmResp),
    SubmitSm(SubmitSm),
    SubmitSmResp(SubmitSmResp),
    DeliverSm(DeliverSm),
    DeliverSmResp(DeliverSmResp),
    Unbind(Unbind),
    UnbindResp(UnbindResp),
    ReplaceSm(ReplaceSm),
    ReplaceSmResp(ReplaceSmResp),
    CancelSm(CancelSm),
    CancelSmResp(CancelSmResp),
    BindTransceiver(BindTransceiver),
    BindTransceiverResp(BindTransceiverResp),
    Outbind(Outbind),
    EnquireLink(EnquireLink),
    EnquireLinkResp(EnquireLinkResp),
    SubmitMulti(SubmitMulti),
    SubmitMultiResp(SubmitMultiResp),
}

实现编解码方法

impl SmppPdu {
    pub fn encode(&self) -> Vec<u8> {
        let mut body_buf = match &self.body {
            SmppBody::BindTransmitter(bind_transmitter) => bind_transmitter.encode(),
            _ => unimplemented!(),
        };

        let command_length = (body_buf.len() + 16) as i32;
        let header = SmppHeader {
            command_length,
            command_id: self.header.command_id,
            command_status: self.header.command_status,
            sequence_number: self.header.sequence_number,
        };

        let mut buf = header.encode();
        buf.append(&mut body_buf);
        buf
    }

    pub fn decode(buf: &[u8]) -> io::Result<Self> {
        let header = SmppHeader::decode(&buf[0..16])?;
        let body = match header.command_id {
            constant::BIND_TRANSMITTER_RESP_ID => SmppBody::BindTransmitterResp(BindTransmitterResp::decode(&buf[16..])?),
            _ => unimplemented!(),
        };
        Ok(SmppPdu { header, body })
    }
}

impl SmppHeader {
    pub(crate) fn encode(&self) -> Vec<u8> {
        let mut buf = vec![];
        buf.extend_from_slice(&self.command_length.to_be_bytes());
        buf.extend_from_slice(&self.command_id.to_be_bytes());
        buf.extend_from_slice(&self.command_status.to_be_bytes());
        buf.extend_from_slice(&self.sequence_number.to_be_bytes());
        buf
    }

    pub(crate) fn decode(buf: &[u8]) -> io::Result<Self> {
        if buf.len() < 16 {
            return Err(io::Error::new(io::ErrorKind::InvalidData, "Buffer too short for SmppHeader"));
        }
        let command_id = u32::from_be_bytes(buf[0..4].try_into().unwrap());
        let command_status = i32::from_be_bytes(buf[4..8].try_into().unwrap());
        let sequence_number = i32::from_be_bytes(buf[8..12].try_into().unwrap());
        Ok(SmppHeader {
            command_length: 0,
            command_id,
            command_status,
            sequence_number,
        })
    }
}

impl BindTransmitter {
    pub(crate) fn encode(&self) -> Vec<u8> {
        let mut buf = vec![];
        write_cstring(&mut buf, &self.system_id);
        write_cstring(&mut buf, &self.password);
        write_cstring(&mut buf, &self.system_type);
        buf.push(self.interface_version);
        buf.push(self.addr_ton);
        buf.push(self.addr_npi);
        write_cstring(&mut buf, &self.address_range);
        buf
    }

    pub(crate) fn decode(buf: &[u8]) -> io::Result<Self> {
        let mut offset = 0;
        let system_id = read_cstring(buf, &mut offset)?;
        let password = read_cstring(buf, &mut offset)?;
        let system_type = read_cstring(buf, &mut offset)?;
        let interface_version = buf[offset];
        offset += 1;
        let addr_ton = buf[offset];
        offset += 1;
        let addr_npi = buf[offset];
        offset += 1;
        let address_range = read_cstring(buf, &mut offset)?;

        Ok(BindTransmitter {
            system_id,
            password,
            system_type,
            interface_version,
            addr_ton,
            addr_npi,
            address_range,
        })
    }
}

实现同步的bind_transmitter方法

pub async fn bind_transmitter(
        &mut self,
        bind_transmitter: BindTransmitter,
    ) -> io::Result<BindTransmitterResp> {
        if let Some(stream) = &mut self.stream {
            let sequence_number = self.sequence_number.next_val();
            let pdu = SmppPdu {
                header: SmppHeader {
                    command_length: 0,
                    command_id: constant::BIND_TRANSMITTER_ID,
                    command_status: 0,
                    sequence_number,
                },
                body: SmppBody::BindTransmitter(bind_transmitter),
            };
            let encoded_request = pdu.encode();
            stream.write_all(&encoded_request).await?;

            let mut length_buf = [0u8; 4];
            stream.read_exact(&mut length_buf).await?;
            let msg_length = u32::from_be_bytes(length_buf) as usize - 4;

            let mut msg_buf = vec![0u8; msg_length];
            stream.read_exact(&mut msg_buf).await?;

            let response = SmppPdu::decode(&msg_buf)?;
            if response.header.command_status != 0 {
                Err(io::Error::new(
                    io::ErrorKind::Other,
                    format!("Error response: {:?}", response.header.command_status),
                ))
            } else {
                // Assuming response.body is of type BindTransmitterResp
                match response.body {
                    SmppBody::BindTransmitterResp(resp) => Ok(resp),
                    _ => Err(io::Error::new(io::ErrorKind::InvalidData, "Unexpected response body")),
                }
            }
        } else {
            Err(io::Error::new(io::ErrorKind::NotConnected, "Not connected"))
        }
    }

运行example，验证连接成功

use smpp_rust::protocol::BindTransmitter;
use smpp_rust::smpp_client::SmppClient;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut client = SmppClient::new("127.0.0.1", 2775);
    client.connect().await?;
    let bind_transmitter = BindTransmitter{
        system_id: "system_id".to_string(),
        password: "password".to_string(),
        system_type: "system_type".to_string(),
        interface_version: 0x34,
        addr_ton: 0,
        addr_npi: 0,
        address_range: "".to_string(),
    };
    client.bind_transmitter(bind_transmitter).await?;
    client.close().await?;
    Ok(())
}

相关开源项目

• netty-codec-sms 存放各种SMS协议（如cmpp、sgip、smpp）的netty编解码器
• sms-client-java 存放各种SMS协议的Java客户端
• sms-server-java 存放各种SMS协议的Java服务端
• smpp-rust smpp协议的rust实现

总结

本文简单对SMPP协议进行了介绍，并尝试用rust实现协议栈，但实际商用发送短信往往更加复杂，面临诸如流控、运营商对接、传输层安全等问题，可以选择华为云消息&短信（Message & SMS）服务通过http协议接入，华为云短信服务是华为云携手全球多家优质运营商和渠道，为企业用户提供的通信服务。企业调用API或使用群发助手，即可使用验证码、通知短信服务。