TCP-IP Management functions

The following functions enable management of TCP-IP sockets for building client or server applications over ETHERNET network:

Functions	Description
tcpAccept	Accept a client connection.
tcpClose	Close a socket.
tcpConnect	Create a client socket and connect it to a server.
tcpIsConnected	Check if a client socket is connected.
tcpIsValid	Check if socket is valid.
tcpListen	Create a listening socket.
tcpReceive	Receive characters.
tcpReceiveArray	Receive characters using array.
tcpSend	Send characters.
tcpSendArray	Send characters using array.

Each socket is identified in the application by a unique handle manipulated as a DINT value.

Attention

Although the system provides a simplified interface, you must be familiar with the socket interface such as existing in other programming languages such as "C".
Socket management may be not available on some targets. Please refer to OEM instructions for further details about available features.

tcpListen: create a listening server socket

SOCK := tcpListen (PORT, MAXCNX);

PORT : DINT    TCP port number to be attached to the server socket.
MAXCNX : DINT  maximum number of client sockets that can be accepted.
SOCK : DINT    ID of the new server socket.

This functions creates a new socket performs the bind and listen operations using default TCP settings. You will have to call the tcpClose function to release the socket returned by this function.

tcpAccept: accept a new client connection

SOCK := tcpAccept (LSOCK);

LSOCK : DINT ID of a server socket returned by the tcpListen function.
SOCK : DINT ID of a new client socket accepted, or invalid ID if no new connection.

This functions performs the accept operation using default TCP settings. You will have to call the tcpClose function to release the socket returned by this function.

tcpConnect: create a client socket and connect it to a server

SOCK := tcpConnect (ADDRESS, PORT);

ADDRESS : STRING IP address of the remote server.
PORT : DINT desired port number on the server.
SOCK : DINT ID of the new client socket.

This functions creates a new socket performs the connect operation using default TCP settings and specified server address and port. You will have to call the tcpClose function to release the socket returned by this function.

Attention

It is possible that the functions returns a valid socket ID even if the connection to the server is not yet actually performed. After calling this function, you must call tcpIsConnected function to know if the connection is ready.

tcpIsConnected: test if a client socket is connected

OK := tcpIsConnected (SOCK);

SOCK : DINT ID of the client socket.
OK : BOOL TRUE if connection is correctly established.

Attention

It is possible that the socket becomes invalid after this function is called, if an error occurs in the TCP connection. You must call the tcpIsValid function after calling this function. If the socket is not valid anymore then you must close it by calling tcpClose.

tcpClose: release a socket

OK := tcpClose (SOCK);

SOCK : DINT ID of any socket.
OK : BOOL TRUE if successful.

You are responsible for closing any socket created by tcpListen, tcpAccept or tcpConnect functions, even if they have become invalid.

tcpSend: send characters

NBSENT := tcpSend (SOCK, NBCHR, DATA);

SOCK : DINT    ID of the socket.
NBCHAR : DINT  number of characters to be sent.
DATA : STRING  string containing characters to send.
NBSENT : DINT  number of characters actually sent.

It is possible that the number of characters actually sent is less than the number expected. In that case, you will have to call again the function on the next cycle to send the pending characters.

Attention

tcpReceive: receive characters

NBRCV := tcpReceive (SOCK, MAXCHR, DATA);

SOCK : DINT    ID of the socket.
MAXCHR : DINT  maximum number of characters desired.
DATA : STRING  string where to store received characters.
NBRCV : DINT   number of characters actually received.

It is possible that the number of characters actually received is less than the number expected. In that case, you will have to call again the function on te next cycle to receive the pending characters.

Attention