PROGRAM TcpServer
VAR_INPUT
nTcp : INT;
Rcv : FB_Fifo999;
sIP : STRING(255) := '192.168.1.11';
IPport : WORD := 5555;
tDelay : TIME := T#100MS;
END_VAR
VAR_OUTPUT
AcceptHl : DINT;
cnt : BOOL;
END_VAR
VAR
ListenHl,Hl : DINT;
Rv0 : BOOL;
ServerAds,AcceptAds : SOCKADDRESS;
ClienSize : DWORD;
sRcv : STRING(255);
RcvNum : DINT;
nNum,n1 : UINT;
bHead : ARRAY [0..5] OF BYTE;
END_VAR

CASE nTcp OF
0://Create handle
ListenHl := SysSockCreate(SOCKET_AF_INET, SOCKET_STREAM,SOCKET_IPPROTO_TCP );
IF ListenHl <> 0 THEN
nTcp := nTcp + 1;
ELSE
nTcp := -1;//create socket error
END_IF
1://Convert IP
ServerAds.sin_addr := SysSockInetAddr(sIP);
ServerAds.sin_port := SysSockHtons(IPport);
ServerAds.sin_family := SOCKET_AF_INET;
nTcp := nTcp + 1;
2://Bind Ip
Rv0 := SysSockBind(ListenHl,ADR(ServerAds),SIZEOF(ServerAds));
IF Rv0 THEN
nTcp := nTcp + 1;
ELSE
nTcp := -2;//Blind ip error
// nTcp := 18;//Blind ip error
END_IF
3://Create listenhandle
Rv0 := SysSockListen(ListenHl , 0 );
IF Rv0 THEN
nTcp := nTcp + 1;
ELSE
nTcp := -3;//listen error
// nTcp := 18;//listen error
END_IF
4://Accept Client
AcceptHl := SysSockAccept(ListenHl, ADR(AcceptAds),ADR(ClienSize));
IF AcceptHl > 0 THEN
SysSockClose(ListenHl);
cnt := TRUE;
nTcp := nTcp + 1;
END_IF
END_CASE

//*****Question*********
The socket is basically created and exploited in the blocking mode. This may cause trouble in PLC
application because the program will stop on the function call where it waits the function finished.
By default, the call of socket function could be blocking for the following “TCP oriented” functions:
SysSockRecv(), SysSockSend(),SysSockConnect(), SysSockAccept(),SysSockClose();

Theoretically, in Data Transfer phase of the TCP connection, the order of call of functions Send() and
Recv() doesn't matter. But, for the same process (task), the sequence:
SysSockRecv();
SysSockSend();
could be critical. The program will not be able to send something if before, it does not receive something.

//*****Question*********
There are different ways to solve this problem in the PLC application:
1. The use of one task for PLC control and some several separate tasks for socket and
communication handling
2. Changing of the socket mode into no blocking mode via function SysSockIoctl()
3. The use the function SysSockSelect()

I tryed the first way using separate tasks and it works.But when there are many clients,it is not good enough.
What I want to know:How to use the way2 and way3?
Would any guys provide code basically on mine?

leon517 hat geschrieben:
PROGRAM TcpServer
VAR_INPUT
nTcp : INT;
Rcv : FB_Fifo999;
sIP : STRING(255) := '192.168.1.11';
IPport : WORD := 5555;
tDelay : TIME := T#100MS;
END_VAR
VAR_OUTPUT
AcceptHl : DINT;
cnt : BOOL;
END_VAR
VAR
ListenHl,Hl : DINT;
Rv0 : BOOL;
ServerAds,AcceptAds : SOCKADDRESS;
ClienSize : DWORD;
sRcv : STRING(255);
RcvNum : DINT;
nNum,n1 : UINT;
bHead : ARRAY [0..5] OF BYTE;
END_VAR
CASE nTcp OF
0://Create handle
ListenHl := SysSockCreate(SOCKET_AF_INET, SOCKET_STREAM,SOCKET_IPPROTO_TCP );
IF ListenHl <> 0 THEN
nTcp := nTcp + 1;
ELSE
nTcp := -1;//create socket error
END_IF
1://Convert IP
ServerAds.sin_addr := SysSockInetAddr(sIP);
ServerAds.sin_port := SysSockHtons(IPport);
ServerAds.sin_family := SOCKET_AF_INET;
nTcp := nTcp + 1;
2://Bind Ip
Rv0 := SysSockBind(ListenHl,ADR(ServerAds),SIZEOF(ServerAds));
IF Rv0 THEN
nTcp := nTcp + 1;
ELSE
nTcp := -2;//Blind ip error
// nTcp := 18;//Blind ip error
END_IF
3://Create listenhandle
Rv0 := SysSockListen(ListenHl , 0 );
IF Rv0 THEN
nTcp := nTcp + 1;
ELSE
nTcp := -3;//listen error
// nTcp := 18;//listen error
END_IF
4://Accept Client
AcceptHl := SysSockAccept(ListenHl, ADR(AcceptAds),ADR(ClienSize));
IF AcceptHl > 0 THEN
SysSockClose(ListenHl);
cnt := TRUE;
nTcp := nTcp + 1;
END_IF
END_CASE
//*****Question********
The socket is basically created and exploited in the blocking mode. This may cause trouble in PLC
application because the program will stop on the function call where it waits the function finished.
By default, the call of socket function could be blocking for the following “TCP oriented” functions:
SysSockRecv(), SysSockSend(),SysSockConnect(), SysSockAccept(),SysSockClose();
Theoretically, in Data Transfer phase of the TCP connection, the order of call of functions Send() and
Recv() doesn't matter. But, for the same process (task), the sequence:
SysSockRecv();
SysSockSend();
could be critical. The program will not be able to send something if before, it does not receive something.
//*****Question********
There are different ways to solve this problem in the PLC application:
1. The use of one task for PLC control and some several separate tasks for socket and
communication handling
2. Changing of the socket mode into no blocking mode via function SysSockIoctl()
3. The use the function SysSockSelect()
I tryed the first way using separate tasks and it works.But when there are many clients,it is not good enough.
What I want to know:How to use the way2 and way3?
Would any guys provide code basically on mine?

Hi, I'm working on a similar project. I have a raspberry in which I need to run a TCP server where I will receive messages from clients by sockets. I can not get it to work properly, have you managed to get it to work properly? Do you have more information on the server?

Thank you very much.