Get PID of an application by its listening TCP port using Win32 API

--- PidByPort.cpp Start ---

#include <winsock2.h>
#include <malloc.h>
#include "iphlpapi_2.h"
#include <stdio.h>

long GetPIDbyPort(long port) {


long ret = 0; PVOID pTCPTable = NULL; DWORD size = 0; DWORD result = 0;    result = pGetExtendedTcpTable(NULL, &size, true, AF_INET, TCP_TABLE_OWNER_MODULE_ALL, 0);  while(result == ERROR_INSUFFICIENT_BUFFER){   
if(pTCPTable != NULL){   
free(pTCPTable); 
}   
pTCPTable = malloc(size);  result = pGetExtendedTcpTable(pTCPTable, &size, true, AF_INET, TCP_TABLE_OWNER_MODULE_ALL, 0);  if(result != NO_ERROR){   
printf("Failed to get TCP Table %s\n", GetLastError()); free(pTCPTable); return ret; 
}   
}  if(result != NO_ERROR){   
printf("Failed to get size estimation %s\n", GetLastError()); return ret; 
}    for(DWORD i = 0; i < ((PMIB_TCPTABLE_OWNER_MODULE)pTCPTable)->dwNumEntries; i++){   
MIB_TCPROW_OWNER_MODULE module = ((PMIB_TCPTABLE_OWNER_MODULE)pTCPTable)->table[i];  if(port==htons((short)module.dwLocalPort)) {   
#ifdef DEBUG  printf("PID = %d, ", module.dwOwningPid); printf("State = %s\n ", g_mibTCPState[module.dwState]); printf(" LocalAddress = %d.%d.%d.%d, ", (htonl(module.dwLocalAddr) >> 24) & 0xFF, (htonl(module.dwLocalAddr) >> 16) & 0xFF, (htonl(module.dwLocalAddr) >> 8)& 0xFF, (htonl(module.dwLocalAddr)) & 0xFF);  printf("LocalPort = %u,\n ", htons((short)module.dwLocalPort));  if(module.dwState != MIB_TCP_STATE_LISTEN){   
printf(" RemoteAddress = %d.%d.%d.%d, ", (htonl(module.dwRemoteAddr) >> 24) & 0xFF, (htonl(module.dwRemoteAddr) >> 16) & 0xFF, (htonl(module.dwRemoteAddr) >> 8) & 0xFF, (htonl(module.dwRemoteAddr)) & 0xFF);  printf("RemotePort = %u\n ", htons((short)module.dwRemotePort)); 
}  printf(" TimeStamp = %I64d, ", module.liCreateTimestamp); printf(" ULONGLONG = UnDocumentedMeaning\n"); printf("\n");  #endif  ret=module.dwOwningPid;   
}   
}  if(pTCPTable != NULL) {   
free(pTCPTable); 
}  return ret;   
} 

--- PidByPort.cpp End --

--- iphlpapi_2.h Start ---

#include <Iprtrmib.h>

char* g_mibTCPState[] =  {
"???",  "MIB_TCP_STATE_CLOSED",  "MIB_TCP_STATE_LISTEN",  "MIB_TCP_STATE_SYN_SENT",  "MIB_TCP_STATE_SYN_RCVD",  "MIB_TCP_STATE_ESTAB",  "MIB_TCP_STATE_FIN_WAIT1",  "MIB_TCP_STATE_FIN_WAIT2",  "MIB_TCP_STATE_CLOSE_WAIT",  "MIB_TCP_STATE_CLOSING",  "MIB_TCP_STATE_LAST_ACK",  "MIB_TCP_STATE_TIME_WAIT",  "MIB_TCP_STATE_DELETE_TCB" }; 
typedef enum {
TCP_TABLE_BASIC_LISTENER,   TCP_TABLE_BASIC_CONNECTIONS,   TCP_TABLE_BASIC_ALL,   TCP_TABLE_OWNER_PID_LISTENER,   TCP_TABLE_OWNER_PID_CONNECTIONS,   TCP_TABLE_OWNER_PID_ALL,   TCP_TABLE_OWNER_MODULE_LISTENER,   TCP_TABLE_OWNER_MODULE_CONNECTIONS,   TCP_TABLE_OWNER_MODULE_ALL } TCP_TABLE_CLASS, *PTCP_TABLE_CLASS; 
DWORD (WINAPI *pGetExtendedTcpTable)(
PVOID pTcpTable,   PDWORD pdwSize,   BOOL bOrder,   ULONG ulAf,   TCP_TABLE_CLASS TableClass,   ULONG Reserved ); 
--- iphlpapi_2.h End---

--- Compiling ---

cl -c PidByPort.cpp /D"_CRT_SECURE_NO_DEPRECATE" /EHcs /DDEBUG

That's it!