Add. Allow get `error` option to socket.

src/options.c

@@ -254,6 +254,19 @@ static int opt_getboolean(lua_State *L, p_socket ps, int level, int name)
     return 1;
 }
 
+int opt_get_error(lua_State *L, p_socket ps)
+{
+  int val = 0;
+  socklen_t len = sizeof(val);
+  if (getsockopt(*ps, SOL_SOCKET, SO_ERROR, (char *) &val, &len) < 0) {
+    lua_pushnil(L);
+    lua_pushstring(L, "getsockopt failed");
+    return 2;
+  }
+  lua_pushstring(L, socket_strerror(val));
+  return 1;
+}
+
 static int opt_setboolean(lua_State *L, p_socket ps, int level, int name)
 {
     int val = auxiliar_checkboolean(L, 3);             /* obj, name, bool */

src/options.h

@@ -42,6 +42,7 @@ int opt_get_linger(lua_State *L, p_socket ps);
 int opt_get_reuseaddr(lua_State *L, p_socket ps);
 int opt_get_ip_multicast_loop(lua_State *L, p_socket ps);
 int opt_get_ip_multicast_if(lua_State *L, p_socket ps);
+int opt_get_error(lua_State *L, p_socket ps);
 
 /* invokes the appropriate option handler */
 int opt_meth_setoption(lua_State *L, p_opt opt, p_socket ps);

src/tcp.c

@@ -73,6 +73,7 @@ static t_opt optget[] = {
     {"reuseaddr",   opt_get_reuseaddr},
     {"tcp-nodelay", opt_get_tcp_nodelay},
     {"linger",      opt_get_linger},
+    {"error",       opt_get_error},
     {NULL,          NULL}
 };
 

src/udp.c

@@ -85,6 +85,7 @@ static t_opt optset[] = {
 static t_opt optget[] = {
     {"ip-multicast-if",    opt_get_ip_multicast_if},
     {"ip-multicast-loop",  opt_get_ip_multicast_loop},
+    {"error",              opt_get_error},
     {NULL,                 NULL}
 };
 

test/test_socket_error.lua

@@ -0,0 +1,27 @@
+local socket = require "socket"
+
+local host, port = "127.0.0.1", "5462"
+
+assert(socket.bind(host, port)):close()
+
+local sock = socket.tcp()
+sock:settimeout(0)
+
+local ok, err = sock:connect(host, port)
+assert(not ok)
+assert('timeout' == err)
+
+for i = 1, 10 do
+  -- select pass even if socket has error
+  local _, rec, err = socket.select(nil, {sock}, 1)
+  assert('timeout' == err)
+  assert(not next(rec))
+  err = sock:getoption("error") -- i get 'connection refused' on WinXP
+  if err then
+    print("Passed! Error is '" .. err .. "'.")
+    os.exit(0)
+  end
+end
+
+print("Fail! No error detected!")
+os.exit(1)