MODBUS_NEW_TCP(3) Libmodbus Manual MODBUS_NEW_TCP(3)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 etablish a connection.
The port argument is the TCP port to use. Set the port to MODBUS_TCP_DEFAULT_PORT to use the default one (502). 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() 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.
EXAMPLE
modbus_t *ctx;
ctx = modbus_new_tcp("127.0.0.1", 1502);
if (ctx == NULL) {
fprintf(stderr, "Unable to allocate libmodbus context
");
return -1;
}
if (modbus_connect(ctx) == -1) {
fprintf(stderr, "Connection failed: %s
", modbus_strerror(errno));
modbus_free(ctx);
return -1;
}
SEE ALSO 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 3.0.3 05/26/2012 MODBUS_NEW_TCP(3)
Check Out this Related Man Page
MODBUS_NEW_RTU(3) Libmodbus Manual MODBUS_NEW_RTU(3)NAME
modbus_new_rtu - create a libmodbus context for RTU
SYNOPSIS
modbus_t *modbus_new_rtu(const char *device, int baud, char parity, int data_bit, int stop_bit);
DESCRIPTION
The modbus_new_rtu() function shall allocate and initialize a modbus_t structure to communicate in RTU mode on a serial line.
The device argument specifies the name of the serial port handled by the OS, eg. /dev/ttyS0 or /dev/ttyUSB0. On Windows, it's necessary to
prepend COM name with \. for COM number greater than 9, eg. \\.\COM10. See
http://msdn.microsoft.com/en-us/library/aa365247(v=vs.85).aspx for details
The baud argument specifies the baud rate of the communication, eg. 9600, 19200, 57600, 115200, etc.
The parity argument can have one of the following values
o N for none
o E for even
o O for odd
The data_bits argument specifies the number of bits of data, the allowed values are 5, 6, 7 and 8.
The stop_bits argument specifies the bits of stop, the allowed values are 1 and 2.
RETURN VALUE
The modbus_new_rtu() 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 argument was given.
EXAMPLE
modbus_t *ctx;
ctx = modbus_new_rtu("/dev/ttyUSB0", 115200, 'N', 8, 1);
if (ctx == NULL) {
fprintf(stderr, "Unable to create the libmodbus context
");
return -1;
}
SEE ALSO modbus_new_tcp(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 3.0.3 05/26/2012 MODBUS_NEW_RTU(3)