SOME/IP-SD -- 协议英文原文讲解5

前言
SOME/IP协议越来越多的用于汽车电子行业中，关于协议详细完全的中文资料却没有，所以我将结合工作经验并对照英文原版协议做一系列的文章。基本分三大块：

1. SOME/IP协议讲解

2. SOME/IP-SD协议讲解

3. python/C++举例调试讲解

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5.1.2.5 Service Entries
find/offer/stop offer Entries 讲解

注：find/offer/stop offer Entries 发出的报文只提供服务ID信息 说明哪个服务可以被订阅，但不提供事件组 即显示哪些事件组可以被订阅 -- 隐藏起来了。所以client订阅时要参照客户发出的矩阵表订阅。

5.1.2.5.1 Find Service Entry
find报文entry

[PRS_SOMEIPSD_00350]
Upstream requirements: RS_SOMEIPSD_00008, RS_SOMEIPSD_00021
The Find Service entry type shall be used for finding service instances and shall
only be sent if the current state of a service is unknown (no current Service Offer was
received and is still valid).
find报文是在没有offer的情况下发出的，否则不能发送find报文了

[PRS_SOMEIPSD_00351]
Upstream requirements: RS_SOMEIPSD_00008, RS_SOMEIPSD_00021
Find Service entries shall set the entry fields in the following way:
• Type shall be set to 0x00 (FindService). -- 固定值
• Service ID shall be set to the Service ID of the service that shall be found.
• Instance ID shall be set to 0xFFFF, if all service instances shall be returned. It
shall be set to the Instance ID of a specific service instance, if just a single service
instance shall be returned.
0xFFFF 找所有的Instance 或是找指定的Instance 前面文章有讲

• Major Version shall be set to 0xFF, that means that services with any version shall
be returned. If set to value different than 0xFF, services with this specific major
version shall be returned only.
匹配所有的主版本号，则设置为0xff,否则设置为需要的版本号

• Minor Version shall be set to 0xFFFF FFFF, that means that services with any
version shall be returned. If set to a value different to 0xFFFF FFFF, services
with this specific minor version shall be returned only.
道理同 上面主版本号，只不过是值大了些

• TTL is not used for FindService entries and can be set to an arbitrary value.The
field is only defined for backward compatibility, and the value shall be ignored by
the receiver of the message.
对于 find报文来说 TTL不用设置 ，接收端应该忽略此值。一般设置为0 就行。

Note: It is expected that the Major Version on client side is configured to a specific
value in normal operation since the client should look for an specific interface version.
Different Major Versions are not compatible to each other.
[PRS_SOMEIPSD_00528]
Upstream requirements: RS_SOMEIPSD_00008, RS_SOMEIPSD_00025
A sender shall not reference Endpoint Options nor Multicast Options in a Find Service
Entry.
find报文不用设置 单播、多播 选项，如果有 接收端应该忽略。
其它选项可以配置

[PRS_SOMEIPSD_00529]
Upstream requirements: RS_SOMEIPSD_00013, RS_SOMEIPSD_00025
A receiver shall ignore Endpoint Options and Multicast Options in a Find Service
Entry.
[PRS_SOMEIPSD_00530]
Upstream requirements: RS_SOMEIPSD_00013, RS_SOMEIPSD_00025
Other Options (neither Endpoint nor Multicast Options), shall still be allowed to be
used in a Find Service Entry.
[PRS_SOMEIPSD_00825]
Upstream requirements: RS_SOMEIPSD_00008, RS_SOMEIPSD_00013
When receiving a FindService Entry the Service ID, Instance ID, Major Version, and
Minor Version shall match exactly to the configured values to identify a Service Instance, except if "any values" are in the Entry (i.e. 0xFFFF for Service ID, 0xFFFF for
Instance ID, 0xFF for Major Version, and 0xFFFFFFFF for Minor Version.)
接收端接收到 find报文，对于entry中的配置项 如果是指定的值 应该精确匹配 成功后再回复offer，否则是通配值 的话就算了

[PRS_SOMEIPSD_00839]
Upstream requirements: RS_SOMEIPSD_00008, RS_SOMEIPSD_00013
If a FindService Entry is received within the Initial Wait Phase for this Server Service
Instance, it shall be ignored.
初始化阶段 收到find 应该忽略 不用先解析 等到初始化完成给回复

5.1.2.5.2 Offer Service Entry

[PRS_SOMEIPSD_00355]
Upstream requirements: RS_SOMEIPSD_00013
The Offer Service entry type shall be used to offer a service to other communication
partners.
[PRS_SOMEIPSD_00356] -- 以下为格式定义 容易理解
Upstream requirements: RS_SOMEIPSD_00013, RS_SOMEIPSD_00025
Offer Service entries shall set the entry fields in the following way:
• Type shall be set to 0x01 (OfferService).
• Service ID shall be set to the Service ID of the service instance offered.
• Instance ID shall be set to the Instance ID of the service instance that is offered.
• Major Version shall be set to the Major Version of the service instance that is
offered.
• Minor Version shall be set to the Minor Version of the service instance that is
offered.
• TTL shall be set to the lifetime of the service instance. After this lifetime the
service instance shall considered not been offered.
offer的有效期 超过后 服务会失效。
• If TTL is set to 0xFFFFFF, the Offer Service entry shall be considered valid until
the next reboot. 长期有效
• If CYCLIC_OFFER_DELAY is defined, TTL shall be greater or equal to the value
for CYCLIC_OFFER_DELAY. 客户指定这个值 则应设置 >=这个值
• TTL shall not be set to 0x000000 since this is considered to be the Stop Offer
Service Entry. 设置为0 表示stop offer 所有offer中不能设置为0.

[PRS_SOMEIPSD_00357]
Upstream requirements: RS_SOMEIPSD_00013, RS_SOMEIPSD_00025
Offer Service entries shall always reference either an IPv4 or IPv6 Endpoint Option to
signal how the service is reachable.
offer应该携带IPv4或IPv6选项 表示服务的发出方式 和 源地址源Port
[PRS_SOMEIPSD_00358]
Upstream requirements: RS_SOMEIPSD_00013, RS_SOMEIPSD_00025
For each Transport Layer Protocol needed for the service (i.e. UDP and/or TCP) an
IPv4 Endpoint option shall be added if IPv4 is supported.
[PRS_SOMEIPSD_00359]
Upstream requirements: RS_SOMEIPSD_00013, RS_SOMEIPSD_00025
For each Transport Layer Protocol needed for the service (i.e. UDP and/or TCP) an
IPv6 Endpoint option shall be added if IPv6 is supported.

[PRS_SOMEIPSD_00826]
Upstream requirements: RS_SOMEIPSD_00012, RS_SOMEIPSD_00013, RS_SOMEIPSD_00025
When receiving the initial OfferService Entry the Service ID, Instance ID, Major Version and Minor Version shall match exactly to the configured values to identify a Service Instance, except if "any values" are in the service configuration (i.e. 0xFFFF for
Instance ID and 0xFFFFFFFF for Minor Version.)
[PRS_SOMEIPSD_00827]
Upstream requirements: RS_SOMEIPSD_00012, RS_SOMEIPSD_00013, RS_SOMEIPSD_-
00025
When receiving a subsequent OfferService Entry or a StopOfferService Entry the
Service ID, Instance ID, Major Version shall match exactly to the values in the initial
OfferService entry to identify a Service Instance.
在收到offer/stopoffer时 要精确匹配Service ID, Instance ID, Major Version 检查是否是自己需要订阅的

注意：sub /suback/ subnack entry 在5.1.3.1章节讲解

5.1.2.5.3 Stop Offer Service Entry

[PRS_SOMEIPSD_00363]
Upstream requirements: RS_SOMEIPSD_00014
The Stop Offer Service entry type shall be used to stop offering service instances.
[PRS_SOMEIPSD_00364]
Upstream requirements: RS_SOMEIPSD_00014
dStop Offer Service entries shall set the entry fields exactly like the Offer Service entry
they are stopping, except:
• TTL shall be set to 0x000000. -- 和offer报文基本一致除了要改TTL为0x000000

[PRS_SOMEIPSD_00840]
Upstream requirements: RS_SOMEIPSD_00014
A StopOfferService (type 0x01), shall carry, i.e. reference, the same options as the
entries trying to stop.

5.1.2.5.4 Usage of Options in Entries 不同类型entries 携带 options数量说明

5.1.2.6 Endpoint Handling for Services and Events -- 针对offer报文的讲解

[PRS_SOMEIPSD_00476]
Upstream requirements: RS_SOMEIPSD_00025
The Service Discovery shall overwrite IP Addresses and Port Numbers with those
transported in Endpoint and Multicast Options if the statically configured values are
different from those in these options.
Note: In other words if a mix of a static and dynamic configuration exists (static configuration that defines the communication endpoints exists and at the same time endpoint
options are exchanged via SD messages at runtime) and the endpoint options in the
static configuration are different from the endpoint options received via SD then the
endpoints options received over SD take precedence over the preconfigured endpoint
options.
SD报文中的IP和PORT 如果和静态配置不一致 则优先动态报文中的 ，并覆盖静态配置
其它 选项 也是优先 动态 覆盖静态

[PRS_SOMEIPSD_00360]
Upstream requirements: RS_SOMEIPSD_00013, RS_SOMEIPSD_00025
The IP addresses and port numbers of the Endpoint Options shall also be used for
transporting events and notification events.
端点选项的ip /port用来 传输 事件、通知。

[PRS_SOMEIPSD_00361]
Upstream requirements: RS_SOMEIPSD_00013, RS_SOMEIPSD_00025
In case of UDP the endpoint option shall be used for the source address and the
source port of the events and notification events, it is also the address the client can
send method requests to.
offer报文中 UDP 端点选项的ip /port用来 传输 事件、通知。同时client也可通过这个IP、PORT请求method
[PRS_SOMEIPSD_00362]
Upstream requirements: RS_SOMEIPSD_00013, RS_SOMEIPSD_00025
In case of TCP the endpoint option shall be used for the IP address and port the client
needs to open a TCP connection in order to receive events using TCP.
接收TCP的事件时 要先 tcp握手建链

[PRS_SOMEIPSD_00801]
Upstream requirements: RS_SOMEIPSD_00013, RS_SOMEIPSD_00025
SOME/IP shall allow services to use UDP and TCP at the same time.
同一个服务 可以同时使用TCP和UDP

[PRS_SOMEIPSD_00802]
Upstream requirements: RS_SOMEIPSD_00013, RS_SOMEIPSD_00025
Which message is sent by which underlying transport protocol shall be determined by
configuration: A Service can use UDP and TCP endpoints at the same time. But per
element of the service it shall to be configured whether TCP or UDP is used.
Note: It needs to be restricted in the configuration which methods and which events
are provided over TCP/UDP. This also means that the same event can not be provided
over TCP and UDP.
虽然可以同时使用TCP和UDP，但是对于具体的event/method/field 只能用一种 不能同时支持。

5.1.2.6.1 Service Endpoints offer报文中 服务端点的讲解

The referenced Endpoint Options of the Offer Service entries denotes the
• IP Address and Port Numbers the service instance is reachable at the server.
• IP Address and Port Numbers the service instance sends the events from.
offfer中的 端点选项中IP、PORT 是可以被访问的 且是用来发送events的，
注：如果这个报文没有events 就不用发送offer

[PRS_SOMEIPSD_00480]
Upstream requirements: RS_SOMEIPSD_00013, RS_SOMEIPSD_00025
Events of this service instance shall not be sent from any other Endpoints than those
given in the Endpoint Options of the Offer Service entries.
事件不能通过除了选项中描述的IP、PORT之外的地址发送。

[PRS_SOMEIPSD_00481]
Upstream requirements: RS_SOMEIPSD_00013, RS_SOMEIPSD_00025
If an ECU offers multiple service instances, SOME/IP messages of these service
instances shall be differentiated by the information transported in the Endpoint Options
referenced by the Offer Service entries.
就算是同一服务的不同instance 在同一个ECU中，端点的IP、PORT也必须不一样。

5.1.2.6.2 Eventgroup Endpoints

[PRS_SOMEIPSD_00484]
Upstream requirements: RS_SOMEIPSD_00015, RS_SOMEIPSD_00025
The Endpoint Options referenced in the Subscribe Eventgroup entries shall also be
used to send unicast UDP or TCP SOME/IP events for this Service Instance.
Thus the Endpoint Options referenced in the Subscribe Eventgroup entries are the IP
Address and the Port Numbers on the client side.

client发送订阅包时，订阅entry对应的Option中的ip/port 是client的，用以发送udp单播或TCP的events

[PRS_SOMEIPSD_00486]
Upstream requirements: RS_SOMEIPSD_00015, RS_SOMEIPSD_00025
TCP events are transported using the TCP connection the client has opened to the
server before sending the Subscribe Eventgroup entry.

如果被订阅的事件是TCP协议类型，则client在发送订阅之前 要先完成TCP的握手建链过程。

[PRS_SOMEIPSD_00487]
Upstream requirements: RS_SOMEIPSD_00015, RS_SOMEIPSD_00025
The initial value of field notifiers (i.e., fields and not pure events) shall be transported
using unicast from Server to Client.
field notifiers 的别订阅后的首次通知 要通过单播、TCP形式发送（单对单）
因为有可能有多个client订阅 如果广播通知的话 会让已经订阅的client端多次收到

[PRS_SOMEIPSD_00488]
Upstream requirements: RS_SOMEIPSD_00015, RS_SOMEIPSD_00025
Subscribe Eventgroup Ack entries shall reference up to 1 Multicast Option for the
Internet Protocol used (IPv4 or IPv6).
suback报文中的 最多只能包含一条 多播option（ipv4/ipv6)

[PRS_SOMEIPSD_00489]
Upstream requirements: RS_SOMEIPSD_00015, RS_SOMEIPSD_00025
The Multicast Option shall be set to UDP as transport protocol.
多播用于UDP -- 前面已经讲过了

[PRS_SOMEIPSD_00490]
Upstream requirements: RS_SOMEIPSD_00015, RS_SOMEIPSD_00025
The client shall open the Endpoint specified in the Multicast Option referenced by the
Subscribe Eventgroup Ack entry as fast as possible to not miss multicast events.
Example: Figure 5.15 shows an example with the different Endpoint and a Multicast
client收到订阅回复中有携带了server events的多播地址时，要尽快配置加入到这个组播中，否则有可能错过组播的事件

Option:
• The Server offers the Service Instance on Server UDP-Endpoint SU and Server
TCP-Endpoint ST
    服务端 offer 提供服务 option中有UDP 也有TCP
• The Client opens a TCP connection client 发起并完成tcp连接
• The Client sends a Subscribe Eventgroup entry with Client UDP-Endpoint CU
(unicast) and a Client TCP-Endpoint CT. client发送订阅报文 携带client的UDP单播 IP+PORT 以及 TCP IP+PORT
• The Server answers with a Subscribe Eventgroup Ack entry with Multicast MU
    服务端单播回复 client 订阅ack 包 ，并携带一个server的组播地址（有的事件要通过组播发送）
Then the following operations happen: 可能会有下面的交互情况
• The Client calls a method on the Server 
  client向server请求method（使用UDP协议 -- 因为假设矩阵中这个Method配置UDP协议）
  
• Request is sent from CU to SU and Response from SU to CU
    server用UDP单播回复
• For TCP this would be: Request dyn to ST and RESPONSE from ST to CT
    也有可能client向server请求TCP协议的method, server通过TCP 回复
• The Server sends a Unicast UDP Event: SU to CU
    server发送UDP单播事件
• The Server sends a Unicast TCP Event: ST to CT
    server发送TCP事件
• The Server sends a Multicast UDP Event: SU to MU
    server发送UDP广播事件
Keep in mind that Multicast Endpoints use a Multicast IP Address on the receiver side,
i.e. the client, and TCP cannot be used for Multicast communication.
    client端配置加入组播 但不能用组播主动发送消息。

注：30490端口号 是协议建议的SOME/IP组播端口号