Siemens AC75 Manual De Usuario

s

AC75_ATC_V01.002

Page 281 of 569

10/30/06

Confidential / Released

-2

Indicates end of data. Data transfer has been finished (all data have been read)

and the service can be closed with 

. 

-1

Applies only to HTTP: Querying number of available bytes is not supported by

the HTTP service. 

0

Indicates that no further data is available at the moment. 

>0

Number of available data bytes. The range is determined by

:

If 

 was greater than 0, then 

 may be

less or equal to the value requested with 

. 

If 

 equals 0 (peek operator) the value indicated by

 may be greater than 1500. 

Indicates whether or not data is available for reading with 

1

Data is available and can be read by sending the 

 command. The

URC appears when less data was confirmed (in 

) than

requested (with 

) during the last "Read Data" operation

and new data is available. 

2

End of data. Data transfer has completed (all data read). The service can be

closed with 

. 

Optional third parameter of the 

 write command response displayed only if the Socket service uses the

UDP protocol. 

The reception of each datagram must be completed before the next datagram can be received. This may be a

problem if the buffer of the host application is limited and not designed to handle the maximum packet size of

1500 bytes. To compensate this, the host is advised to request, via 

, an amount less or

equal its maxmimum buffer capacity and wait for the resulting 

 write command response with param-

eter 

. The benefit of this approach is that the host may properly receive all parts

of a UDP datagram, as after each received data part the number of remaining bytes is synchronized, until read-

ing the datagram is finished.

If the currently read datagram is smaller than the number of bytes requested by the host the 

 parameter is omitted. 

Further write attempts with 

 are denied as long as the 

 is unequal 0 or

is not omitted. In this case the service returns 

0

Indicates that all bytes of the current UDP datagram are read. 

1...(max. data size)-1

Indicates that the currently read UDP datagram is not yet complete. The dis-

played value is the remaining number of bytes. 

 is unequal 0 until reading all parts of the cur-

rent datagram is finished. 

Service specific parameter of the 

 write command response. If the Socket service is configured as UDP

endpoint this parameter returns the IP address and the UDP port of the remote host that has sent the current

UDP data. 

<cnfReadLength>

(num)

<urcCauseId>

(num)

<remainUdpPacketLength>

(num)

<optServParm>

(str)