mongoose/docs/overview/conn-flags.md

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Connection flags

Each connection has a flags bit field. Some flags are set by Mongoose, for example if a user creates an outbound UDP connection using a udp://1.2.3.4:5678 address, Mongoose is going to set a MG_F_UDP flag for that connection. Other flags are meant to be set only by the user event handler to tell Mongoose how to behave. Below is a list of connection flags that are meant to be set by event handlers:

• MG_F_FINISHED_SENDING_DATA tells Mongoose that all data has been appended to the send_mbuf. As soon as Mongoose sends it to the socket, the connection will be closed.
• MG_F_BUFFER_BUT_DONT_SEND tells Mongoose to append data to the send_mbuf but hold on sending it, because the data will be modified later and then will be sent by clearing the MG_F_BUFFER_BUT_DONT_SEND flag.
• MG_F_CLOSE_IMMEDIATELY tells Mongoose to close the connection immediately, usually after an error.
• MG_F_USER_1, MG_F_USER_2, MG_F_USER_3, MG_F_USER_4 could be used by a developer to store an application-specific state.

Flags below are set by Mongoose:

• MG_F_SSL_HANDSHAKE_DONE SSL only, set when SSL handshake is done.
• MG_F_CONNECTING set when the connection is in connecting state after mg_connect() call but connect did not finish yet.
• MG_F_LISTENING set for all listening connections.
• MG_F_UDP set if the connection is UDP.
• MG_F_IS_WEBSOCKET set if the connection is a WebSocket connection.
• MG_F_WEBSOCKET_NO_DEFRAG should be set by a user if the user wants to switch off automatic WebSocket frame defragmentation.