SOMEIP学习总结（包含VSOMEIP库）
一.基本概念
1.SOMEIP支持TCP和UDP两种传输方式
其中，SOMEIP-SD的消息都是通过UDP发送的
2.SOMEIP支持如下中间件特性：
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Serialization – transforming into and from on-wire representation.
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Remote Procedure Call (RPC) and Messaging – implementing remote invocation of functions as well as other messages.
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Service Discovery (SD) – dynamically finding and functionality and configuring its access.
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Publish/Subscribe (Pub/Sub) – dynamically configuring which data is needed and shall be sent to the client.
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Segmentation of UDP messages – allowing the transport of large SOME/IP messages over UDP without the need of fragmentation.
3.Remote Procedure Call (RPC) and Messaging支持下列消息
- Request/Response Methods: A request sent from a client to the server and a response sent back from server to client. Additionally, SOME/IP allows error responses to be sent back from server to client instead of the regular response. This feature might be used to implement a different payload format in error cases.
- Fire and Forget Methods: A request is sent from a client to the server.
- Event: An event is sent from the server to a relevant clients. Which client needs this event will be determined via SOME/IP-SD.
- Field: A field can have an option notifier (event to be sent cyclically or on-change), an optional setter (a request/response method to update the field), and an optional getter (a request/response method to read out the current value of the field.)
4.服务和事件组的关系
5.Magic Cookie的作用
当SOMEIP在TCP传输写一下，当发生流错误时，可以通过magic cookie找到流中下一条报文的开头位置
6.SOMEIP-SD消息的结构
7.Entry携带Option的内容
8.停止OfferService的方式
Offer和StopOffer的SD报文中，service entry的type都是1（offer），唯一不同的是TTL，在停止service的offer时，发布的SD报文中，service entry的ttl值为0
9.SOMEIP普通消息的结构
10.消息头中的Message Type字段的含义
可以看到，Message Type字段（一个字节）的第七个BIT位是TP FLAG，当使用UDP传输并且payload超过1400字节时，会启用TP传输，此时，Message Type字段的TP FLAG会变成1
https://www.some-ip.com/details.shtml
https://blog.csdn.net/Aliven888/article/details/123333466
