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Man Pages


Manual Reference Pages  -  MODBUS_NEW_TCP (3)

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NAME

modbus_new_tcp - create a libmodbus context for TCP/IPv4

CONTENTS

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\(cqs convenient to use a port number greater than or equal to 1024 because it\(cqs 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\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_rtu(3) modbus_free(3)

AUTHORS

The libmodbus documentation was written by St\(&#146;ephane Raimbault <\m[blue]stephane.raimbault@gmail.com\m[][1]>

NOTES

1. stephane.raimbault@gmail.com  mailto:stephane.raimbault@gmail.com
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libmodbus 3&.1&.0 MODBUS_NEW_TCP (3) 10/06/2013

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