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2.Data handling and data segmentation in TCP socket interface transmission and reception

a.When using the TCP socket interface for data transmission, the data transmitted in a single operation is handled by the receive side Ethernet Port as one section of a continuous data stream that comes from the sender. (See figure 6.6.)

In this technique, the data is not handled as a single unit, as it is in UDP socket interface transmission.

b.The amount of data transmitted to the T2N from the TCP socket interface due to a T2N receive request will vary depending on both the timing with which the T2N issues the receive request, and the timing with which the data arrives at the TCP socket interface.

c.In the Ethernet Port TCP socket interface, up to 4380 bytes of received data can be stored per socket. Also note that up to 2000 bytes of data can be transferred to the T2N for a single receive request from the T2N. For example, if the remote port sends 800 bytes at a time, then the amount of received data per socket may be either 800, 1600, 2400, 3200, or 4000 bytes. If the amount of received data is 800 or 1600 bytes, those 800 or 1600 bytes can be acquired by the T2N by a receive request from the T2N. In cases where the amount of received data is 2400, 3200, or 4000 bytes, 2000 bytes will be transferred by the first receive request from the T2N, and the remaining 400, 1200, or 2000 bytes can be transferred by issuing another receive request from the T2N.

d.Therefore, to handle one unit of transmitted data as a single unit of data on the receiving side as well, at the system design stage users must analyze both the data format (head/tail delimiting codes, data sequencing) and the amount of data to be transmitted, and provide routines to decode the transmitted data in the receiving T2N user software.

e.Allocate an area one word larger than the transmitted data size as the T2N register area that will hold the received data. As the result of a receive request, information indicating the size of the transmitted data for the single operation plus the data transmitted in the single operation will be stored in that area.

Transmitted data

Ethernet Port TCP socket interface

Consecutive data (up to 4380 bytes)

Data received up to this time

Max: 2000 bytes

Receive response

T2N

Receive request

Data received by the T2N

Transferred data

Figure 6.6 Handling of Transmitted Data in the TCP Socket Interface

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Toshiba T2N instruction manual Handling of Transmitted Data in the TCP Socket Interface