Replying to a message

The attributes that can be sent in reply to a message are as follows:

res
A string that's identical to the value of the msg attribute of the message this is a response to.
id
A string that is identical to the value of the id attribute of the message this is a response to.
dat
Other data that is associated with the response. This attribute is optional. The dat attribute is frequently JSON-encoded because there is often a need to encode more than a simple string.
err
If present, this indicates that the request failed. It should be the number of the error as defined in errno.h. For example, for EBUSY you would put 16 in this field.
errstr
An optional string that could contain further explanation of the error or debugging information. For example, a more verbose explanation might be required for an error resulting from a request that includes a SQL statement, since errors might occur for diverse reasons.