本文分享自华为云社区《华为云短信服务教你用Zig实现Cmpp协议》，作者： 张俭。

引言&协议概述

中国网络通信集团短信网关协议（CNGP）是中国网通为实现短信业务而制定的一种通信协议，全称叫做China Netcom Short Message Gateway Protocol，用于在PHS短消息网关（SMGW）和服务提供商（SP）之间、短消息网关（SMGW）和短消息网关（SMGW）之间通信。

Zig 是一种性能优异、安全性高的系统编程语言，适合用于实现底层网络协议。它提供了强大的类型系统、编译时计算和错误处理机制。

CNGP 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）先和短信网关（SMGW Short Message Gateway）建立起 TCP 长连接，并使用 CNGP 命令与SMGW进行交互，实现短信的发送和接收。在CNGP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

连接成功，发送短信

连接成功，从SMGW接收到短信

协议帧介绍

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

CNGP Header

Header包含以下字段，大小长度都是4字节

• Total Length：整个PDU的长度，包括Header和Body。
• Command ID：用于标识PDU的类型（例如，Login、Submit等）。
• Common Status：命令状态
• Sequence Id：序列号，用来匹配请求和响应。

使用Zig实现CNGP协议栈里的建立连接

. ├── src │ └── bound_atomic.zig │ ├── cngp_client.zig │ ├── cngp_client_login_example.zig │ ├── constant.zig │ ├── protocol.zig

• bound_atomic.zig：原子递增工具类，用来做SequenceId
• cngp_client.zig：这个文件包含Cngp的定义，该类负责与CNGP服务进行通信，例如建立连接、发送短信等
• cngp_client_login_example.zig：示例代码
• constant.zig：存放常量
• protocol.zig：这个文件包含 CNGP 协议相关的定义和实现，例如协议的命令 ID、PDU 格式等。

constant.zig存放相关commandId

pub const CommandId = enum(u32) { Login = 0x00000001, LoginResp = 0x80000001, Submit = 0x00000002, SubmitResp = 0x80000002, Deliver = 0x00000003, DeliverResp = 0x80000003, ActiveTest = 0x00000004, ActiveTestResp = 0x80000004, Exit = 0x00000006, ExitResp = 0x80000006, };

protocol.zig协议编解码

const std = @import("std"); const io = std.io; const CommandId = @import("constant.zig").CommandId; pub const CngpLogin = struct { clientId: []const u8, authenticatorClient: []const u8, loginMode: u8, timeStamp: i32, version: u8, pub fn length(self: *const CngpLogin) usize { return self.clientId.len + self.authenticatorClient.len + 1 + 4 + 1; } pub fn encode(self: *const CngpLogin, writer: anytype) !void { try writer.writeAll(self.clientId); try writer.writeAll(self.authenticatorClient); try writer.writeByte(self.loginMode); try writer.writeIntBig(i32, self.timeStamp); try writer.writeByte(self.version); } }; pub const CngpLoginResp = struct { authenticatorServer: []const u8, version: u8, pub fn decode(buffer: []u8) !CngpLoginResp { var stream = std.io.fixedBufferStream(buffer); var reader = stream.reader(); var authenticatorServerBuffer: [16]u8 = undefined; var fixedSize = try reader.read(&authenticatorServerBuffer); if (fixedSize != 16) { return error.InvalidLength; } const version = try reader.readByte(); return CngpLoginResp{ .authenticatorServer = authenticatorServerBuffer[0..], .version = version, }; } }; pub const CngpHeader = struct { total_length: i32, command_id: CommandId, command_status: i32, sequence_id: i32, }; pub const CngpBody = union(enum) { Login: CngpLogin, LoginResp: CngpLoginResp, }; pub const CngpPdu = struct { header: CngpHeader, body: CngpBody, pub fn length(self: *const CngpPdu) usize { return 16 + switch (self.body) { .Login => |login| login.length(), else => 0, }; } pub fn encode(self: *const CngpPdu) ![]u8 { const len = self.length(); var buffer = try std.heap.page_allocator.alloc(u8, len); var stream = std.io.fixedBufferStream(buffer); var writer = stream.writer(); try writer.writeInt(i32, @as(i32, @intCast(len)), .Big); try writer.writeInt(u32, @intFromEnum(self.header.command_id), .Big); try writer.writeInt(i32, self.header.command_status, .Big); try writer.writeInt(i32, self.header.sequence_id, .Big); switch (self.body) { .Login => |login| try login.encode(writer), else => unreachable, } return buffer; } pub fn decode_login_resp(buffer: []u8) !CngpPdu { var header: CngpHeader = undefined; header.total_length = 0; header.command_id = CommandId.LoginResp; header.command_status = std.mem.readIntLittle(i32, buffer[8..12]); header.sequence_id = std.mem.readIntLittle(i32, buffer[12..16]); const body = try CngpLoginResp.decode(buffer[12..]); return CngpPdu{ .header = header, .body = CngpBody{ .LoginResp = body }, }; } };

利用原子类型实现sequenceId递增

const std = @import("std"); pub const BoundAtomic = struct { min: i32, max: i32, integer: std.atomic.Atomic(i32), pub fn new(min: i32, max: i32) BoundAtomic { return BoundAtomic{ .min = min, .max = max, .integer = std.atomic.Atomic(i32).init(min), }; } pub fn nextVal(self: *BoundAtomic) i32 { while (true) { const current = self.integer.load(.SeqCst); const next = if (current == self.max) self.min else current + 1; if (self.integer.compareAndSwap(current, next, .SeqCst, .SeqCst) == null) { return next; } } } };

实现client以及login方法

const std = @import("std"); const net = std.net; const CngpBody = @import("protocol.zig").CngpBody; const CngpLogin = @import("protocol.zig").CngpLogin; const CngpPdu = @import("protocol.zig").CngpPdu; const CommandId = @import("constant.zig").CommandId; const BoundAtomic = @import("bound_atomic.zig").BoundAtomic; pub const CngpClient = struct { host: []const u8, port: u16, sequenceId: BoundAtomic, stream: ?std.net.Stream, pub fn init(host: []const u8, port: u16) CngpClient { return CngpClient{ .host = host, .port = port, .sequenceId = BoundAtomic.new(1, 0x7FFFFFFF), .stream = null, }; } pub fn connect(self: *CngpClient) !void { const peer = try net.Address.parseIp4(self.host, self.port); self.stream = try net.tcpConnectToAddress(peer); } pub fn login(self: *CngpClient, body: CngpLogin) !CngpPdu { const sequenceId = self.sequenceId.nextVal(); const pdu = CngpPdu{ .header = .{ .total_length = 0, // Will be calculated in encode method .command_id = CommandId.Login, .command_status = 0, .sequence_id = sequenceId, }, .body = CngpBody{ .Login = body }, }; const data = try pdu.encode(); if (self.stream) |s| { const size = try s.write(data); if (size != data.len) { return error.WriteFailed; } var buffer: [4]u8 = undefined; const readLengthSize = try s.read(buffer[0..]); if (readLengthSize != 4) { return error.ReadFailed; } const remainLength = std.mem.readInt(u32, buffer[0..], .Big) - 4; var responseBuffer = try std.heap.page_allocator.alloc(u8, remainLength); defer std.heap.page_allocator.free(responseBuffer); var reader = s.reader(); const readSize = try reader.read(responseBuffer[0..remainLength]); if (readSize != remainLength) { return error.ReadFailed; } const response = try CngpPdu.decode_login_resp(responseBuffer); return response; } else { return error.UnexpectedNull; } } pub fn close(self: *CngpClient) void { if (self.stream) |s| { s.close(); self.stream = null; } } };

运行Example，验证连接成功

const std = @import("std"); const CngpClient = @import("cngp_client.zig").CngpClient; const CngpLogin = @import("protocol.zig").CngpLogin; pub fn main() !void { const host = "127.0.0.1"; const port: u16 = 9890; var client = CngpClient.init(host, port); defer client.close(); const clientId = "1234567890"; const authenticatorClient = "1234567890123456"; const loginMode: u8 = 1; const timeStamp: i32 = 123456789; const version: u8 = 1; const loginBody = CngpLogin{ .clientId = clientId, .authenticatorClient = authenticatorClient, .loginMode = loginMode, .timeStamp = timeStamp, .version = version, }; try client.connect(); const response = try client.login(loginBody); try std.io.getStdOut().writer().print("Login response: {}\n", .{response}); }

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
• cmpp-python cmpp协议的python实现
• cngp-zig cmpp协议的python实现
• smpp-rust smpp协议的rust实现

总结

本文简单对CNGP协议进行了介绍，并尝试用zig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，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。

 

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