mongo通信协议

先是一个包头：

struct MsgHeader {
    int32   messageLength; // total message size, including this
    int32   requestID;     // identifier for this message
    int32   responseTo;    // requestID from the original request
                           //   (used in responses from db)
    int32   opCode;        // request type - see table below for details
}

特点：每个请求都有个id，客户端启动的时候从0开始递增

opCode表示操作类型，根据这个处理后面真正的请求

比如查询包：

struct OP_QUERY {
    MsgHeader header;                 // standard message header
    int32     flags;                  // bit vector of query options.  See below for details.
    cstring   fullCollectionName ;    // "dbname.collectionname"
    int32     numberToSkip;           // number of documents to skip
    int32     numberToReturn;         // number of documents to return
                                      //  in the first OP_REPLY batch
    document  query;                  // query object.  See below for details.
  [ document  returnFieldsSelector; ] // Optional. Selector indicating the fields
                                      //  to return.  See below for details.
}

抓包情况如下：

一目了然。

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官网：https://docs.mongodb.com/manual/reference/mongodb-wire-protocol/