When I use modbus tcp master mode, how do I know that the slave has closed the connection?

[jhembed]

When I use modbus tcp master mode, how do I know that the slave has closed the connection?

[oe5hpm]

once "modbus_receive" returns -1 you can be sure that the connection is dead ....

you have to close the active socket like this: close(modbus_get_socket(tcp_srv_mb));