text: <user>
  Create a function block for TCP/IP communication in TwinCAT Structured Text using the TF6310 TCP/IP server<|endoftext|>
  <assistant>
  FUNCTION_BLOCK FB_TCPClient
  VAR_INPUT
      sIPAddress      : STRING;   // IP address of the target server
      nPort           : UINT;     // Port number of the target server
      bConnect        : BOOL;     // Trigger to establish connection
      bSend           : BOOL;     // Trigger to send data
      sDataToSend     : STRING;   // Data to be sent
  END_VAR
  
  VAR_OUTPUT
      bConnected      : BOOL;     // Connection status
      bError          : BOOL;     // Error flag
      nErrorID        : UDINT;    // Error ID
      sReceivedData   : STRING;   // Received data from server
  END_VAR
  
  VAR
      fbConnect       : FB_SocketConnect;
      fbSend          : FB_SocketSend;
      fbReceive       : FB_SocketReceive;
      fbClose         : FB_SocketClose;
      hSocket         : T_HSOCKET;
      buffer          : ARRAY[0..255] OF BYTE;
      cbReceived      : UDINT;
      state           : INT := 0;
      timer           : TON;
  END_VAR
  
  // Main program logic
  CASE state OF
      0:  // Idle state
          IF bConnect THEN
              fbConnect(
                  sSrvNetId:= '', 
                  sRemoteHost:= sIPAddress, 
                  nRemotePort:= nPort,
                  bExecute:= TRUE,
                  tTimeout:= T#5S,
                  hSocket=> hSocket
              );
              state := 1;
          END_IF
  
      1:  // Connecting
          fbConnect(bExecute := FALSE);
          IF NOT fbConnect.bBusy THEN
              IF NOT fbConnect.bError THEN
                  bConnected := TRUE;
                  state := 2;
              ELSE
                  bError := TRUE;
                  nErrorID := fbConnect.nErrId;
                  state := 0;
              END_IF
          END_IF
  
      2:  // Connected, ready to send/receive
          IF bSend THEN
              fbSend(
                  sSrvNetId:= '', 
                  hSocket:= hSocket,
                  pSrc:= ADR(sDataToSend),
                  cbLen:= LEN(sDataToSend),
                  bExecute:= TRUE,
                  tTimeout:= T#5S
              );
              state := 3;
          END_IF
  
          // Always try to receive data
          fbReceive(
              sSrvNetId:= '', 
              hSocket:= hSocket,
              pDest:= ADR(buffer),
              cbLen:= SIZEOF(buffer),
              bExecute:= TRUE,
              tTimeout:= T#0S
          );
  
          IF fbReceive.nRecBytes > 0 THEN
              sReceivedData := LEFT(STRING(pBuffer := ADR(buffer), nMaxSize := SIZEOF(buffer)), fbReceive.nRecBytes);
          END_IF
  
      3:  // Sending data
          fbSend(bExecute := FALSE);
          IF NOT fbSend.bBusy THEN
              IF fbSend.bError THEN
                  bError := TRUE;
                  nErrorID := fbSend.nErrId;
              END_IF
              state := 2;
          END_IF
  
  END_CASE
  
  // Error handling and connection timeout
  IF bError OR timer.Q THEN
      fbClose(
          sSrvNetId:= '', 
          hSocket:= hSocket,
          bExecute:= TRUE
      );
      bConnected := FALSE;
      state := 0;
  END_IF
  
  timer(IN:= state > 0, PT:= T#60S);
  
  This function block (FB_TCPClient) implements a TCP/IP client using TwinCAT 3's TF6310 TCP/IP server. It provides functionality to connect to a server, send data, and receive data asynchronously. The FB adheres to IEC 61131-3 standards and is optimized for the TwinCAT 3 environment.
  
  Key features:
  1. Asynchronous connection handling
  2. Data sending and receiving capabilities
  3. Error handling and timeout mechanism
  4. State machine implementation for clear program flow
  
  To enhance this implementation, consider the following TwinCAT 3 features:
  1. Use of TcUnit for unit testing the function block
  2. Implementation of a circular buffer for more efficient data handling
  3. Integration with TwinCAT HMI for visual representation of the TCP/IP communication status<|endoftext|>
  