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MODBUS_NEW_TCP_PI(3) Libmodbus Manual MODBUS_NEW_TCP_PI(3)
NAME
modbus_new_tcp_pi - create a libmodbus context for TCP Protocol
Independent
SYNOPSIS
modbus_t *modbus_new_tcp_pi(const char *node, const char *service);
DESCRIPTION
The modbus_new_tcp_pi() function shall allocate and initialize a
modbus_t structure to communicate with a Modbus TCP IPv4 or Ipv6
server.
The node argument specifies the host name or IP address of the host to
connect to, eg. 192.168.0.5 , ::1 or server.com.
The service argument is the service name/port number to connect to. To
use the default Modbus port use the string "502". On many Unix systems,
it's convenient to use a port number greater than or equal to 1024
because it's not necessary to have administrator privileges.
RETURN VALUE
The modbus_new_tcp_pi() 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
The node string is empty or has been truncated. The service string
is empty or has been truncated.
EXAMPLE
modbus_t *ctx;
ctx = modbus_new_tcp_pi("::1", "1502");
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_new_tcp(3) modbus_new_rtu(3) modbus_free(3)
AUTHORS
The libmodbus documentation was written by Stephane Raimbault
<stephane.raimbault@gmail.com[1]>
NOTES
1. stephane.raimbault@gmail.com
mailto:stephane.raimbault@gmail.com
libmodbus 3.1.0 10/06/2013 MODBUS_NEW_TCP_PI(3)