Teach "pigs" to use the Unix socket

pigs.c

@@ -37,6 +37,7 @@ This version is for pigpio version 69+
 #include <unistd.h>
 #include <sys/socket.h>
 #include <sys/types.h>
+#include <sys/un.h>
 #include <netdb.h>
 #include <arpa/inet.h>
 
@@ -109,7 +110,29 @@ static int initOpts(int argc, char *argv[])
 
 static int openSocket(void)
 {
-   int sock, err;
+   int sock;
+   const char *sockStr;
+
+   sockStr = getenv(PI_ENVSOCK);
+   if (sockStr && *sockStr)
+   {
+      struct sockaddr_un addr;
+      addr.sun_family = AF_LOCAL;
+      strncpy (addr.sun_path, sockStr, sizeof (addr.sun_path));
+      addr.sun_path[sizeof (addr.sun_path) - 1] = 0;
+      sock = socket (AF_LOCAL, SOCK_STREAM, 0);
+      if (sock > -1)
+      {
+         if (connect (sock, (struct sockaddr *) &addr, sizeof (addr)) == -1)
+         {
+            close(sock);
+            sock = -1;
+         }
+      }
+   }
+   else
+   {
+      int err;
       struct addrinfo hints, *res, *rp;
       const char *addrStr, *portStr;
 
@@ -141,8 +164,8 @@ static int openSocket(void)
       }
 
       freeaddrinfo(res);
-
       if (rp == NULL) return SOCKET_OPEN_FAILED;
+   }
 
    return sock;
 }