Coap blockwise 传输：如何将以下块映射到初始 block/request

Question

假设我有一个客户端想要向服务器发送两个大请求（同时）。

假设第一个有效载荷是 "ABCD"，第二个有效载荷是 "WXYZ"。

第一个请求的第一个块具有 messageID=1 和 token=0x1，负载 "AB"，

第二个请求的第一个块具有 messageID=2 和 token=0x2，负载 "WX"，

第一个请求的第二个块具有 messageID=3 和 token=0x3，负载 "CD"，

第二个请求的第二个块具有 messageID=4 和 token=0x4，负载 "YZ"。

你可以看到我的目标。如果每个请求的 messageID 和 token 都不同，并且它们不是连续的，那么服务器应该如何连接正确的块？

这是一个序列图：

   CLIENT                                                   SERVER
     |                                                        |
     | CON [MID=1,TOK=1], POST, /foo, 1:0/1/128, "AB" ------> |
     |                                                        |
     | <------   ACK [MID=1,TOK=1], 2.31 Continue, 1:0/1/128  |
     |                                                        |
     | CON [MID=2,TOK=2], POST, /foo, 1:0/1/128, "WX" ------> |
     |                                                        |
     | <------   ACK [MID=2,TOK=2], 2.31 Continue, 1:0/1/128  |
     |                                                        |
     | CON [MID=3,TOK=3], POST, /foo, 1:1/0/128, "CD" ------> |
     |                                                        |
     | <------   ACK [MID=3,TOK=3], 2.01 Created, 1:1/0/128   |
     |                                                        |
     | CON [MID=4,TOK=4], POST, /foo, 1:1/0/128, "YZ" ------> |
     |                                                        |
     | <------   ACK [MID=4,TOK=4], 2.01 Created, 1:1/0/128   |

问题出现在消息 3 上：服务器现在有两个不完整的负载，它如何可靠地将第三个请求映射到正确的负载？它怎么知道有效负载应该是 "ABCD" 而不是 "WXCD"？

分块传输的规范仅说明如下：

As a general comment on tokens, there is no other mention of tokens in this document, as block-wise transfers handle tokens like any other CoAP exchange. As usual the client is free to choose tokens for each exchange as it likes.

Answer 1

你是对的，事实上 block-wise specs 突出显示它并提出一个解决方法（仅针对 block2 选项）：

The Block2 option provides no way for a single endpoint to perform multiple concurrently proceeding block-wise response payload transfer (e.g., GET) operations to the same resource. This is rarely a requirement, but as a workaround, a client may vary the cache key (e.g., by using one of several URIs accessing resources with the same semantics, or by varying a proxy-safe elective option).

和：

The Block1 option provides no way for a single endpoint to perform multiple concurrently proceeding block-wise request payload transfer (e.g., PUT or POST) operations to the same resource. Starting a new block-wise sequence of requests to the same resource (before an old sequence from the same endpoint was finished) simply overwrites the context the server may still be keeping. (This is probably exactly what one wants in this case - the client may simply have restarted and lost its knowledge of the previous sequence.)

Coap blockwise 传输：如何将以下块映射到初始 block/request

Coap blockwise transfer: How to map following blocks to initial block/request

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