Getting TCP statistics

Sample code

The following sample code shows how to use GetTcpStatistics().

#include <stdio.h>

#include <winsock2.h>
#include <iphlpapi.h>

int
main()
{
 MIB_TCPSTATS tcpstats;

 if (GetTcpStatistics(&tcpstats) == NOERROR) {
   printf("dwRtoAlgorithm: %ld\n", tcpstats.dwRtoAlgorithm);
   printf("dwRtoMin:       %ld\n", tcpstats.dwRtoMin);
   printf("dwRtoMax:       %ld\n", tcpstats.dwRtoMax);
   printf("dwMaxConn:      %ld\n", tcpstats.dwMaxConn);
   printf("dwActiveOpens:  %ld\n", tcpstats.dwActiveOpens);
   printf("dwPassiveOpens: %ld\n", tcpstats.dwPassiveOpens);
   printf("dwAttemptFails: %ld\n", tcpstats.dwAttemptFails);
   printf("dwEstabResets:  %ld\n", tcpstats.dwEstabResets);
   printf("dwCurrEstab:    %ld\n", tcpstats.dwCurrEstab);
   printf("dwInSegs:       %ld\n", tcpstats.dwInSegs);
   printf("dwOutSegs:      %ld\n", tcpstats.dwOutSegs);
   printf("dwRetransSegs:  %ld\n", tcpstats.dwRetransSegs);
   printf("dwInErrs:       %ld\n", tcpstats.dwInErrs);
   printf("dwOutRsts:      %ld\n", tcpstats.dwOutRsts);
   printf("dwNumConns:     %ld\n", tcpstats.dwNumConns);
 } else {
   printf("GetTcpStatistics failed : %d\n", GetLastError());
 }

 return 0;
}

Sample code output

The sample will output an message like the following.

C:> a.exe
dwRtoAlgorithm: 4
dwRtoMin:       300
dwRtoMax:       120000
dwMaxConn:      -1
dwActiveOpens:  832
dwPassiveOpens: 10
dwAttemptFails: 0
dwEstabResets:  29
dwCurrEstab:    0
dwInSegs:       487549
dwOutSegs:      253735
dwRetransSegs:  0
dwInErrs:       0
dwOutRsts:      71
dwNumConns:     5

Structure used by GetTcpStatistics()

The following structure is MIB_TCPSTATS that is used by GetTcpStatistics().

typedef struct _MIB_TCPSTATS {
  DWORD dwRtoAlgorithm;
  DWORD dwRtoMin;
  DWORD dwRtoMax;
  DWORD dwMaxConn;
  DWORD dwActiveOpens;
  DWORD dwPassiveOpens;
  DWORD dwAttemptFails;
  DWORD dwEstabResets;
  DWORD dwCurrEstab;
  DWORD dwInSegs;
  DWORD dwOutSegs;
  DWORD dwRetransSegs;
  DWORD dwInErrs;
  DWORD dwOutRsts;
  DWORD dwNumConns;
} MIB_TCPSTATS, *PMIB_TCPSTATS;

dwRtoAlgorithm	RTO(Retransmission Time-Out) Algorithm Type MIB_TCP_RTO_CONSTANT Constant Time-out MIB_TCP_RTO_RSRE MIL-STD-1778 Appendix B MIB_TCP_RTO_VANJ Van Jacobson's Algorithm MIB_TCP_RTO_OTHER Other
dwRtoMin	Minimum RTO. msec.
dwRtoMax	Maximum RTO. msec.
dwMaxConn	Maximum number of connections. When -1, variable length.
dwActiveOpens	Number of Active Open. Number of connections that are in initialization state.
dwPassiveOpens	Number of Passive Open. Number of listen state.
dwAttemptFails	Number of failed connections.
dwEstabResets	Number of reset connections.
dwCurrEstab	Number of connections that are currently established.
dwInSegs	Number of segments received.
dwOutSegs	Number of segments sent.
dwRetransSegs	Number of retransmitted segments.
dwInErrs	Number of errors received.
dwOutRsts	Number of segments with RST flag.
dwNumConns	Number of all connections. The listen state connections are not be included.