GetTcpTable2 function

The GetTcpTable2 function retrieves the IPv4 TCP connection table.

Syntax

ULONG GetTcpTable2(
  PMIB_TCPTABLE2 TcpTable,
  PULONG         SizePointer,
  BOOL           Order
);

Parameters

TcpTable

A pointer to a buffer that receives the TCP connection table as a MIB_TCPTABLE2 structure.

SizePointer

On input, specifies the size of the buffer pointed to by the TcpTable parameter.

On output, if the buffer is not large enough to hold the returned connection table, the function sets this parameter equal to the required buffer size.

Order

A value that specifies whether the TCP connection table should be sorted. If this parameter is TRUE, the table is sorted in the order of:

  1. Local IP address
  2. Local port
  3. Remote IP address
  4. Remote port

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 TcpTable parameter is not large enough. The required size is returned in the PULONG variable pointed to by the SizePointer parameter.

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

ERROR_INVALID_PARAMETER
The SizePointer parameter is NULL, or GetTcpTable2 is unable to write to the memory pointed to by the SizePointer parameter.
ERROR_NOT_SUPPORTED
This function is not supported on the operating system in use on the local system.
Other
Use FormatMessage to obtain the message string for the returned error.

Remarks

The GetTcpTable2 function is defined on Windows Vista and later.

The GetTcpTable2 function is an enhanced version of the GetTcpTable function that also retrieves information on the TCP offload state of the TCP connection.

Examples

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

C++
#include <winsock2.h>
#include <ws2tcpip.h>
#include <iphlpapi.h>
#include <stdio.h>

// Need to link with Iphlpapi.lib and Ws2_32.lib #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_TCPTABLE2 pTcpTable;
ULONG ulSize = 0;
DWORD dwRetVal = 0;

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

struct in_addr IpAddr;

int i;

pTcpTable = (MIB_TCPTABLE2 *) MALLOC(sizeof (MIB_TCPTABLE2));
if (pTcpTable == NULL) {
    printf("Error allocating memory\n");
    return 1;
}

ulSize = sizeof (MIB_TCPTABLE);

// Make an initial call to GetTcpTable2 to // get the necessary size into the ulSize variable if ((dwRetVal = GetTcpTable2(pTcpTable, &ulSize, TRUE)) == ERROR_INSUFFICIENT_BUFFER) { FREE(pTcpTable); pTcpTable = (MIB_TCPTABLE2 *) MALLOC(ulSize); if (pTcpTable == NULL) { printf("Error allocating memory\n"); return 1; } } // Make a second call to GetTcpTable2 to get // the actual data we require if ((dwRetVal = GetTcpTable2(pTcpTable, &ulSize, TRUE)) == NO_ERROR) { printf("\tNumber of entries: %d\n", (int) pTcpTable->dwNumEntries); for (i = 0; i < (int) pTcpTable->dwNumEntries; i++) { printf("\n\tTCP[%d] State: %ld - ", i, pTcpTable->table[i].dwState); switch (pTcpTable->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; } IpAddr.S_un.S_addr = (u_long) pTcpTable->table[i].dwLocalAddr; strcpy_s(szLocalAddr, sizeof (szLocalAddr), inet_ntoa(IpAddr)); printf("\tTCP[%d] Local Addr: %s\n", i, szLocalAddr); printf("\tTCP[%d] Local Port: %d \n", i, ntohs((u_short)pTcpTable->table[i].dwLocalPort));

        IpAddr.S_un.S_addr = (u_long) pTcpTable-&gt;table[i].dwRemoteAddr;
        strcpy_s(szRemoteAddr, sizeof (szRemoteAddr), inet_ntoa(IpAddr));
        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));
               
        printf("\tTCP[%d] Owning PID: %d\n", i, pTcpTable-&gt;table[i].dwOwningPid);
        printf("\tTCP[%d] Offload State: %ld - ", i,
               pTcpTable-&gt;table[i].dwOffloadState);
        switch (pTcpTable-&gt;table[i].dwOffloadState) {
        case TcpConnectionOffloadStateInHost:
            printf("Owned by the network stack and not offloaded \n");
            break;
        case TcpConnectionOffloadStateOffloading:
            printf("In the process of being offloaded\n");
            break;
        case TcpConnectionOffloadStateOffloaded:
            printf("Offloaded to the network interface control\n");
            break;
        case TcpConnectionOffloadStateUploading:
            printf("In the process of being uploaded back to the network stack \n");
            break;
        default:
            printf("UNKNOWN Offload state value\n");
            break;
        }
               
    }
} else {
    printf("\tGetTcpTable2 failed with %d\n", dwRetVal);
    FREE(pTcpTable);
    return 1;
}

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

return 0;    

}

Requirements

   
Windows version Windows Vista [desktop apps only] Windows Server 2008 [desktop apps only]
Target Platform Windows
Header iphlpapi.h
Library Iphlpapi.lib
DLL Iphlpapi.dll

See Also

GetExtendedTcpTable

GetOwnerModuleFromTcpEntry

GetTcp6Table

GetTcpStatistics

GetTcpStatisticsEx

GetTcpTable

MIB_TCP6ROW2

MIB_TCP6TABLE

MIB_TCP6TABLE2

MIB_TCP6TABLE_OWNER_MODULE

MIB_TCP6TABLE_OWNER_PID

MIB_TCPROW

MIB_TCPROW2

MIB_TCPROW_OWNER_MODULE

MIB_TCPROW_OWNER_PID

MIB_TCPTABLE

MIB_TCPTABLE2

MIB_TCPTABLE_OWNER_MODULE

MIB_TCPTABLE_OWNER_PID

SetTcpEntry