MODBUS TCP with multiple nodes

User 10265805

I'm working on win ce 6 modbus tcp client server, application is developed for a client server communication and it is working fine. now req is my slave device should respond to the diff slave addresses polled by master/client. Can I just change slave id and establish connection or I need to close previous connection and again establish new one below is the code, which is working fine for one node, if I polled with other node ID then it gives exception. what change it req to communicate with other node simultaneously. My device should be able to communicate with 32 diff nodes on modbus tcp. Shall I create individual threads for each node but how they will communicate on same port? before establishing connection with other node shall I close previous node?

startupServer(int slaveAddr, const TCHAR * const hostName)
{

int result;
int tcpOption;
struct sockaddr_in hostAddress;

if (isStarted())
return (FTALK_ILLEGAL_STATE_ERROR);

// Note: For TCP we allow 0 as slave address, -1 means ignore slave adr
if ((slaveAddr < -1) || (slaveAddr > 255))
return (FTALK_ILLEGAL_ARGUMENT_ERROR);
this->slaveAddr = slaveAddr;

//
// Special treatment for the Win32 platform, needs to load WinSock DLL
//
#ifdef _WINSOCKAPI_
WSADATA wsaData;

result = WSAStartup(0x0101, &wsaData);
if (result != 0)
return (FTALK_SOCKET_LIB_ERROR);
#endif

//
// Open socket
//
listenSocket = socket(PF_INET, SOCK_STREAM, 0);
if (listenSocket == INVALID_SOCKET)
{
shutdownServer();
return (FTALK_OPEN_ERR);
}

//
// Configure listen socket options (we ignore errors here)
//
#ifdef SO_REUSEADDR
tcpOption = 1; // Enable option
setsockopt(listenSocket, SOL_SOCKET, SO_REUSEADDR,
(char *) &tcpOption, sizeof (tcpOption));
#endif

//
// Binding the listen socket to the port
//
hostAddress.sin_family = AF_INET;
if ((hostName == NULL) || (hostName[0] == '\0'))
hostAddress.sin_addr.s_addr = htonl(INADDR_ANY);
else
{
hostAddress.sin_addr.s_addr = inet_addr((char *) hostName);
#if !defined(__VXWORKS__) // We don't support host name resolving with VxWorks
if (hostAddress.sin_addr.s_addr == INADDR_NONE)
{
struct hostent *hostInfo;

     hostInfo = gethostbyname((char \*) hostName);

     if (hostInfo == NULL)
        return (FTALK\_TCPIP\_CONNECT\_ERR);
     hostAddress.sin\_addr = \*(struct in\_addr \*) hostIn

Lost User

You already posted this in the C++ forum. Please do not crosspost.

Veni, vidi, abiit domum

Sunasara Imdadhusen

please try to post minimum code to get higher chance for getting answer from the experts, because on one has time to read your thousands lines of code.