Question

What is the easiest way to get a PID that listens on a given port in C#? Basically, I want to make sure that my service is running and listens on a port I have provided it. If there is an easier way than parsing netstat output it will be great.

Answer 1

from win XP SP2 onwards you can P/Invoke to GetExtendedTcpTable

Using This person’s kind work to flesh out the signature (the PInvoke.net spec is incomplete) here is a (rough and poor at error checking) example

using System; using System.Runtime.InteropServices;  public enum TCP_TABLE_CLASS : int {     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 }   [StructLayout(LayoutKind.Sequential)] public struct MIB_TCPROW_OWNER_PID {     public uint state;     public uint localAddr;     public byte localPort1;     public byte localPort2;     public byte localPort3;     public byte localPort4;     public uint remoteAddr;     public byte remotePort1;     public byte remotePort2;     public byte remotePort3;     public byte remotePort4;     public int owningPid;      public ushort LocalPort {         get         {             return BitConverter.ToUInt16(                 new byte[2] { localPort2, localPort1}, 0);         }     }      public ushort RemotePort     {         get         {             return BitConverter.ToUInt16(                 new byte[2] { remotePort2, remotePort1}, 0);         }     } }  [StructLayout(LayoutKind.Sequential)] public struct MIB_TCPTABLE_OWNER_PID {     public uint dwNumEntries;     MIB_TCPROW_OWNER_PID table; }  [DllImport('iphlpapi.dll', SetLastError=true)] static extern uint GetExtendedTcpTable(IntPtr pTcpTable,      ref int dwOutBufLen,      bool sort,      int ipVersion,      TCP_TABLE_CLASS tblClass,     int reserved);  public static MIB_TCPROW_OWNER_PID[] GetAllTcpConnections() {     MIB_TCPROW_OWNER_PID[] tTable;     int AF_INET = 2;    // IP_v4     int buffSize = 0;      // how much memory do we need?     uint ret = GetExtendedTcpTable(IntPtr.Zero,          ref buffSize,          true,          AF_INET,          TCP_TABLE_CLASS.TCP_TABLE_OWNER_PID_ALL,         0);             if (ret != 0 && ret != 122) // 122 insufficient buffer size         throw new Exception('bad ret on check ' + ret);     IntPtr buffTable = Marshal.AllocHGlobal(buffSize);      try     {         ret = GetExtendedTcpTable(buffTable,              ref buffSize,              true,              AF_INET,              TCP_TABLE_CLASS.TCP_TABLE_OWNER_PID_ALL,              0);         if (ret != 0)             throw new Exception('bad ret '+ ret);                  // get the number of entries in the table         MIB_TCPTABLE_OWNER_PID tab =              (MIB_TCPTABLE_OWNER_PID)Marshal.PtrToStructure(                 buffTable,                  typeof(MIB_TCPTABLE_OWNER_PID));          IntPtr rowPtr = (IntPtr)((long)buffTable +               Marshal.SizeOf(tab.dwNumEntries));         tTable = new MIB_TCPROW_OWNER_PID[tab.dwNumEntries];          for (int i = 0; i < tab.dwNumEntries; i++)         {             MIB_TCPROW_OWNER_PID tcpRow = (MIB_TCPROW_OWNER_PID)Marshal                 .PtrToStructure(rowPtr, typeof(MIB_TCPROW_OWNER_PID));             tTable[i] = tcpRow;             // next entry             rowPtr = (IntPtr)((long)rowPtr + Marshal.SizeOf(tcpRow));            }     }     finally     {         // Free the Memory         Marshal.FreeHGlobal(buffTable);     }     return tTable; }