1MODBUS_TCP_LISTEN(3)           libmodbus Manual           MODBUS_TCP_LISTEN(3)
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NAME

6       modbus_tcp_listen - create and listen a TCP Modbus socket (IPv4)
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SYNOPSIS

9       int modbus_tcp_listen(modbus_t *ctx, int nb_connection);
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DESCRIPTION

12       The modbus_tcp_listen() function shall create a socket and listen to
13       maximum nb_connection incoming connections on the specified IP address.
14       The context _ctx _must be allocated and initialized with
15       modbus_new_tcp(3) before to set the IP address to listen, if IP address
16       is set to NULL or 0.0.0.0, any addresses will be listen.
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RETURN VALUE

19       The function shall return a new socket if successful. Otherwise it
20       shall return -1 and set errno.
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EXAMPLE

23       For detailed examples, see source files in tests directory:
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25       •   unit-test-server.c, simple but handle only one connection
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27       •   bandwidth-server-many-up.c, handles several connections at once
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29           ...
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31           /* To listen any addresses on port 502 */
32           ctx = modbus_new_tcp(NULL, 502);
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34           /* Handle until 10 established connections */
35           server_socket = modbus_tcp_listen(ctx, 10);
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37           /* Clear the reference set of socket */
38           FD_ZERO(&refset);
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40           /* Add the server socket */
41           FD_SET(server_socket, &refset);
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43           if (select(server_socket + 1, &refset, NULL, NULL, NULL) == -1) {
44           }
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46           ...
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48           close(server_socket);
49           modbus_free(ctx);
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SEE ALSO

52       modbus_new_tcp(3) modbus_tcp_accept(3) modbus_tcp_pi_listen(3)
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AUTHORS

55       The libmodbus documentation was written by Stéphane Raimbault
56       <stephane.raimbault@gmail.com>
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60libmodbus v3.1.6                  01/19/2023              MODBUS_TCP_LISTEN(3)