=== JSON-RPC 

==== struct mg_rpc_request

[source,c]
----
struct mg_rpc_request {
  struct json_token *message; /* Whole RPC message */
  struct json_token *id;      /* Message ID */
  struct json_token *method;  /* Method name */
  struct json_token *params;  /* Method params */
};
----
JSON-RPC request 

==== struct mg_rpc_reply

[source,c]
----
struct mg_rpc_reply {
  struct json_token *message; /* Whole RPC message */
  struct json_token *id;      /* Message ID */
  struct json_token *result;  /* Remote call result */
};
----
JSON-RPC response 

==== struct mg_rpc_error

[source,c]
----
struct mg_rpc_error {
  struct json_token *message;       /* Whole RPC message */
  struct json_token *id;            /* Message ID */
  struct json_token *error_code;    /* error.code */
  struct json_token *error_message; /* error.message */
  struct json_token *error_data;    /* error.data, can be NULL */
};
----
JSON-RPC error 

==== mg_rpc_parse_reply()

[source,c]
----
int mg_rpc_parse_reply(const char *buf, int len, struct json_token *toks,
                       int max_toks, struct mg_rpc_reply *,
                       struct mg_rpc_error *);
----
Parse JSON-RPC reply contained in `buf`, `len` into JSON tokens array
`toks`, `max_toks`. If buffer contains valid reply, `reply` structure is
populated. The result of RPC call is located in `reply.result`. On error,
`error` structure is populated. Returns: the result of calling
`parse_json(buf, len, toks, max_toks)`:

On success, an offset inside `json_string` is returned
where parsing has finished. On failure, a negative number is
returned, one of:

- `#define JSON_STRING_INVALID           -1`
- `#define JSON_STRING_INCOMPLETE        -2`
- `#define JSON_TOKEN_ARRAY_TOO_SMALL    -3` 

==== mg_rpc_create_request()

[source,c]
----
int mg_rpc_create_request(char *buf, int len, const char *method,
                          const char *id, const char *params_fmt, ...);
----
Create JSON-RPC request in a given buffer.

Return length of the request, which
can be larger then `len` that indicates an overflow.
`params_fmt` format string should conform to `json_emit()` API,
see https://github.com/cesanta/frozen 

==== mg_rpc_create_reply()

[source,c]
----
int mg_rpc_create_reply(char *buf, int len, const struct mg_rpc_request *req,
                        const char *result_fmt, ...);
----
Create JSON-RPC reply in a given buffer.

Return length of the reply, which
can be larger then `len` that indicates an overflow.
`result_fmt` format string should conform to `json_emit()` API,
see https://github.com/cesanta/frozen 

==== mg_rpc_create_error()

[source,c]
----
int mg_rpc_create_error(char *buf, int len, struct mg_rpc_request *req,
                        int code, const char *message, const char *fmt, ...);
----
Create JSON-RPC error reply in a given buffer.

Return length of the error, which
can be larger then `len` that indicates an overflow.
`fmt` format string should conform to `json_emit()` API,
see https://github.com/cesanta/frozen 

==== mg_rpc_create_std_error()

[source,c]
----
int mg_rpc_create_std_error(char *buf, int len, struct mg_rpc_request *req,
                            int code);
----
Create JSON-RPC error in a given buffer.

Return length of the error, which
can be larger then `len` that indicates an overflow. See
JSON_RPC_*_ERROR definitions for standard error values:

- `#define JSON_RPC_PARSE_ERROR (-32700)`
- `#define JSON_RPC_INVALID_REQUEST_ERROR (-32600)`
- `#define JSON_RPC_METHOD_NOT_FOUND_ERROR (-32601)`
- `#define JSON_RPC_INVALID_PARAMS_ERROR (-32602)`
- `#define JSON_RPC_INTERNAL_ERROR (-32603)`
- `#define JSON_RPC_SERVER_ERROR (-32000)` 

==== mg_rpc_dispatch()

[source,c]
----
int mg_rpc_dispatch(const char *buf, int, char *dst, int dst_len,
                    const char **methods, mg_rpc_handler_t *handlers);
----
Dispatches a JSON-RPC request.

Parses JSON-RPC request contained in `buf`, `len`.
Then, dispatches the request to the correct handler method.
Valid method names should be specified in NULL
terminated array `methods`, and corresponding handlers in `handlers`.
Result is put in `dst`, `dst_len`. Return: length of the result, which
can be larger then `dst_len` that indicates an overflow.
Overflown bytes are not written to the buffer.
If method is not found, an error is automatically generated.