modbus_new_tcp(3) [debian man page]
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)
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MODBUS_REPLY_EXCEPTI(3) Libmodbus Manual MODBUS_REPLY_EXCEPTI(3) NAME
modbus_reply_exception - send an exception reponse SYNOPSIS
*int modbus_reply_exception(modbus_t *ctx, const uint8_t *req, unsigned int exception_code); DESCRIPTION
The modbus_reply_exception() function shall send an exception response based on the exception_code in argument. The libmodbus provides the following exception codes: o MODBUS_EXCEPTION_ILLEGAL_FUNCTION (1) o MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS (2) o MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE (3) o MODBUS_EXCEPTION_SLAVE_OR_SERVER_FAILURE (4) o MODBUS_EXCEPTION_ACKNOWLEDGE (5) o MODBUS_EXCEPTION_SLAVE_OR_SERVER_BUSY (6) o MODBUS_EXCEPTION_NEGATIVE_ACKNOWLEDGE (7) o MODBUS_EXCEPTION_MEMORY_PARITY (8) o MODBUS_EXCEPTION_NOT_DEFINED (9) o MODBUS_EXCEPTION_GATEWAY_PATH (10) o MODBUS_EXCEPTION_GATEWAY_TARGET (11) The initial request req is required to build a valid response. RETURN VALUE
The modbus_reply_exception() function shall return the length of the response sent if successful. Otherwise it shall return -1 and set errno. ERRORS
EINVAL The exception code is invalid SEE ALSO
modbus_reply(3) libmodbus(7) 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_REPLY_EXCEPTI(3)