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modbus_new_tcp() modbus_new_tcp() Name modbus_new_tcp - create a libmodbus context for TCP/IPv4 Synopsis modbus_t *modbus_new_tcp(const char *ip, int port); Description The modbus_new_tcp() function shall allocate and initialize a modbus_t structure to communicate with a Modbus TCP IPv4 server. The ip argument specifies the IP address of the server to which the client wants to establish a connection. A NULL value can be used to listen on any addresses in server mode. The port argument is the TCP port to use. Set the port to MODBUS_TCP_DE- FAULT_PORT to use the default one (502). It's convenient to use a port num- ber greater than or equal to 1024 because it's not necessary to have admin- istrator privileges. Return value The function shall return a pointer to a modbus_t structure if successful. Otherwise it shall return NULL and set errno to one of the values defined below. Errors * EINVAL, an invalid IP address was given. * ENOMEM, out of memory. Possibly, the application hits its memory limit and/or whole system is running out of memory. Example modbus_t *ctx; ctx = modbus_new_tcp("127.0.0.1", 502); if (ctx == NULL) { fprintf(stderr, "Unable to allocate libmodbus context\n"); return -1; } if (modbus_connect(ctx) == -1) { fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno)); modbus_free(ctx); return -1; } See also * modbus_tcp_listen <modbus_tcp_listen.md> * modbus_free <modbus_free.md> modbus_new_tcp()
Name | Synopsis | Description | Return value | Errors | Example | See also
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