At the bottom is the clip I stubbed out, but it's basically a PROGRAM code-block called DoTransaction that moves the .Command and .Response members into/out of an OutBuff and InBuff data blocks before it does the STREAMOUT and STREAMIN.
Look at the attachment for the .PDF of the Ladder Logic where the STREAMOUT and STREAMIN are done. Note how in Rung #2 I move the structure's .Command WORD to OutBuff0:UW, then I use 2 BYTES of OutBuff0 in my STREAMOUT. Similarly, in the corresponding STREAMIN instruction I use 2 BYTEs of InBuff0, then in rung #44 I move those 2 BYTEs of OutBuff0:UW to the structure's .Response WORD. InBuff and OutBuff are both BYTE blocks, each 8 bytes long, and that is what I use in the STREAMIN and STREAMOUT instructions (since I can't use the structure members).
From $Main, just RUN DoTransaction, then look for DoTransaction.Done then check MyTCP.Success vs. MyTCP.Fail.
// Ver(103) PCU(4) Do-more Designer Clip Source Project: C:\Do-more\Designer2_1\Projects\TCPProtoStruct1 Format: Do-more Designer 2.00+ DO-MORE Ladder
PLC BX-DM1E-18ED13
$PRGRM DoTransaction
SG DoTransaction.S0
RST MyTCP.Success
RST MyTCP.Fail
MOVE MyTCP.Command OutBuff0:W
OPENTCP @MyTCPClient -1062666239 12345 0x101 DoTransaction.S1 DoTransaction.S99
SG DoTransaction.S1
STREAMOUT @MyTCPClient 0x1 SS0 OutBuff0 2 0x100 0x101 DoTransaction.S2 DoTransaction.S99
SG DoTransaction.S2
STREAMIN @MyTCPClient 2 0x0 1000 0x1 SS0 InBuff0 2 D100 0x0 0x101 DoTransaction.S3 DoTransaction.S99
SG DoTransaction.S3
MOVE InBuff0:W MyTCP.Response
SET MyTCP.Success
EXIT
SG DoTransaction.S99
SET MyTCP.Fail
EXIT
$PGMEND DoTransaction
#BEGIN DEVICE
@MyTCPClient, 32769, 8
#END
#BEGIN UDT_CONFIG
TCPProtoStruct
// Field Name, Data Type, Memory Layout, Read/Write, Display Format, Data View Detail
Command, UWORD, 0:0, Read-Write, Native, Short
Response, UWORD, 0:1, Read-Write, Native, Short
ACKResp, UWORD, 1:0, Read-Write, Native, Short
NAKResp, UWORD, 1:1, Read-Write, Native, Short
Success, BIT, 2:0, Read-Write, Native, Short
Fail, BIT, 2:1, Read-Write, Native, Short
#END
#BEGIN MEM_CONFIG
InBuff UBYTE decimal 8
OutBuff UBYTE decimal 8
MyTCP TCPProtoStruct 0
DoTransaction PROGRAM 0 -1
#END