GetTcpTable function

The GetTcpTable function retrieves the IPv4 TCP connection table.

Syntax

ULONG GetTcpTable(
  PMIB_TCPTABLE TcpTable,
  PULONG        SizePointer,
  BOOL          Order
);

Parameters

TcpTable

TBD

SizePointer

TBD

Order

TBD

Return Value

If the function succeeds, the return value is NO_ERROR.

If the function fails, the return value is one of the following error codes.

Return code Description
ERROR_INSUFFICIENT_BUFFER
The buffer pointed to by the pTcpTable parameter is not large enough. The required size is returned in the DWORD variable pointed to by the pdwSize parameter.

This error is also returned if the pTcpTable parameter is NULL.

ERROR_INVALID_PARAMETER
The pdwSize parameter is NULL, or GetTcpTable is unable to write to the memory pointed to by the pdwSize parameter.
ERROR_NOT_SUPPORTED
This function is not supported on the operating system in use on the local system.
STATUS_UNSUCCESSFUL
If you receive this return code then calling the function again is usually enough to clear the issue and get the desired result. This return code can be a consequence of the system being under high load. For example, if the size of the TCP connection table changes by more than 2 additional items 3 consecutive times.
Other
Use FormatMessage to obtain the message string for the returned error.

Remarks

On the Windows SDK released for Windows Vista and later, the return value from the GetTcpTable function is changed to a data type of ULONG which is equivalent to a DWORD.

Examples

The following example retrieves the TCP connection table for IPv4 and prints the state of each connection.

C++
// Need to link with Iphlpapi.lib and Ws2_32.lib
#include <winsock2.h>
#include <ws2tcpip.h>
#include <iphlpapi.h>
#include <stdio.h>

#pragma comment(lib, "iphlpapi.lib") #pragma comment(lib, "ws2_32.lib")

#define MALLOC(x) HeapAlloc(GetProcessHeap(), 0, (x)) #define FREE(x) HeapFree(GetProcessHeap(), 0, (x))

/* Note: could also use malloc() and free() */

int main() {

// Declare and initialize variables
PMIB_TCPTABLE pTcpTable;
DWORD dwSize = 0;
DWORD dwRetVal = 0;

char szLocalAddr[128];
char szRemoteAddr[128];

struct in_addr IpAddr;

int i;

pTcpTable = (MIB_TCPTABLE *) MALLOC(sizeof (MIB_TCPTABLE));
if (pTcpTable == NULL) {
    printf("Error allocating memory\n");
    return 1;
}

dwSize = sizeof (MIB_TCPTABLE);

// Make an initial call to GetTcpTable to // get the necessary size into the dwSize variable if ((dwRetVal = GetTcpTable(pTcpTable, &dwSize, TRUE)) == ERROR_INSUFFICIENT_BUFFER) { FREE(pTcpTable); pTcpTable = (MIB_TCPTABLE *) MALLOC(dwSize); if (pTcpTable == NULL) { printf("Error allocating memory\n"); return 1; } } // Make a second call to GetTcpTable to get // the actual data we require if ((dwRetVal = GetTcpTable(pTcpTable, &dwSize, TRUE)) == NO_ERROR) { printf("\tNumber of entries: %d\n", (int) pTcpTable->dwNumEntries); for (i = 0; i < (int) pTcpTable->dwNumEntries; i++) { IpAddr.S_un.S_addr = (u_long) pTcpTable->table[i].dwLocalAddr; strcpy_s(szLocalAddr, sizeof (szLocalAddr), inet_ntoa(IpAddr)); IpAddr.S_un.S_addr = (u_long) pTcpTable->table[i].dwRemoteAddr; strcpy_s(szRemoteAddr, sizeof (szRemoteAddr), inet_ntoa(IpAddr));

        printf("\n\tTCP[%d] State: %ld - ", i,
               pTcpTable-&gt;table[i].dwState);
        switch (pTcpTable-&gt;table[i].dwState) {
        case MIB_TCP_STATE_CLOSED:
            printf("CLOSED\n");
            break;
        case MIB_TCP_STATE_LISTEN:
            printf("LISTEN\n");
            break;
        case MIB_TCP_STATE_SYN_SENT:
            printf("SYN-SENT\n");
            break;
        case MIB_TCP_STATE_SYN_RCVD:
            printf("SYN-RECEIVED\n");
            break;
        case MIB_TCP_STATE_ESTAB:
            printf("ESTABLISHED\n");
            break;
        case MIB_TCP_STATE_FIN_WAIT1:
            printf("FIN-WAIT-1\n");
            break;
        case MIB_TCP_STATE_FIN_WAIT2:
            printf("FIN-WAIT-2 \n");
            break;
        case MIB_TCP_STATE_CLOSE_WAIT:
            printf("CLOSE-WAIT\n");
            break;
        case MIB_TCP_STATE_CLOSING:
            printf("CLOSING\n");
            break;
        case MIB_TCP_STATE_LAST_ACK:
            printf("LAST-ACK\n");
            break;
        case MIB_TCP_STATE_TIME_WAIT:
            printf("TIME-WAIT\n");
            break;
        case MIB_TCP_STATE_DELETE_TCB:
            printf("DELETE-TCB\n");
            break;
        default:
            printf("UNKNOWN dwState value\n");
            break;
        }
        printf("\tTCP[%d] Local Addr: %s\n", i, szLocalAddr);
        printf("\tTCP[%d] Local Port: %d \n", i,
               ntohs((u_short)pTcpTable-&gt;table[i].dwLocalPort));
        printf("\tTCP[%d] Remote Addr: %s\n", i, szRemoteAddr);
        printf("\tTCP[%d] Remote Port: %d\n", i,
               ntohs((u_short)pTcpTable-&gt;table[i].dwRemotePort));
    }
} else {
    printf("\tGetTcpTable failed with %d\n", dwRetVal);
    FREE(pTcpTable);
    return 1;
}

if (pTcpTable != NULL) {
    FREE(pTcpTable);
    pTcpTable = NULL;
}    

return 0;    

}

Requirements

   
Windows version Windows 2000 Professional [desktop apps UWP apps] Windows 2000 Server [desktop apps UWP apps]
Target Platform Windows
Header iphlpapi.h
Library Iphlpapi.lib
DLL Iphlpapi.dll

See Also

GetExtendedTcpTable

GetOwnerModuleFromTcpEntry

GetTcp6Table

GetTcp6Table2

GetTcpStatistics

GetTcpStatisticsEx

GetTcpTable2

MIB_TCPROW

MIB_TCPROW_OWNER_MODULE

MIB_TCPROW_OWNER_PID

MIB_TCPTABLE

MIB_TCPTABLE_OWNER_MODULE

MIB_TCPTABLE_OWNER_PID

SetTcpEntry