Technical data

W&T

Subject to errors and modifications

Socket-Interface

IP-Header

Ethernet-Header Ethernet-Data

IO-Structures

UDP-/TCP-DataUDP-/TCP-Header

IP-Data

Which of the two protocols are used, UDP or TCP, depends on

the type of application. Both protocols offer advantages and

disadvantages which must be considered depending on the

application you want to create.

Help with socket programming including the basics of

TCP/IP can be found in a short and clear form in our

manual „Ready in 1 day for TCP/IP Sockets“. Program examples

for client/server applications under TCP/IP are located on our

homepage at http://www.wut.de.

3.8.7 Definition of the IO structures

To be able to unambiguously identify and process the contents

of a packet, in BINARY mode all the data must be sent to the

Web-IO in the form of these IO structures regardless of whether

50xxx-compatible or Socket Client mode is used..

All structures begin with the same header which consists of the

following 4 WORDS (16bit_Integer):

Structure-Header WORD send_sequence always 0

WORD rec_sequence always 0

WORD struct_type identifies the structure

WORD length length of the structure in bytes

send_sequence, rec_sequence

For compatibilty reasons with respect to older Digital I/O Com-

Servers send_sequence and rec_sequence are provided but not

used. Both values are always 0.

struct_type

The value struct_type identifies which structure is being used.

Both the PC application and the Web-IO decide when the data

are received how the structure should be processed based on

the value struct_type.