diff --git a/pgconn/auth_scram.go b/pgconn/auth_scram.go
index 37b602d6..6ca9e337 100644
--- a/pgconn/auth_scram.go
+++ b/pgconn/auth_scram.go
@@ -80,12 +80,14 @@ func (c *PgConn) rxSASLContinue() (*pgproto3.AuthenticationSASLContinue, error)
 	if err != nil {
 		return nil, err
 	}
-	saslContinue, ok := msg.(*pgproto3.AuthenticationSASLContinue)
-	if ok {
-		return saslContinue, nil
+	switch m := msg.(type) {
+	case *pgproto3.AuthenticationSASLContinue:
+		return m, nil
+	case *pgproto3.ErrorResponse:
+		return nil, ErrorResponseToPgError(m)
 	}
 
-	return nil, errors.New("expected AuthenticationSASLContinue message but received unexpected message")
+	return nil, fmt.Errorf("expected AuthenticationSASLContinue message but received unexpected message %T", msg)
 }
 
 func (c *PgConn) rxSASLFinal() (*pgproto3.AuthenticationSASLFinal, error) {
@@ -93,12 +95,14 @@ func (c *PgConn) rxSASLFinal() (*pgproto3.AuthenticationSASLFinal, error) {
 	if err != nil {
 		return nil, err
 	}
-	saslFinal, ok := msg.(*pgproto3.AuthenticationSASLFinal)
-	if ok {
-		return saslFinal, nil
+	switch m := msg.(type) {
+	case *pgproto3.AuthenticationSASLFinal:
+		return m, nil
+	case *pgproto3.ErrorResponse:
+		return nil, ErrorResponseToPgError(m)
 	}
 
-	return nil, errors.New("expected AuthenticationSASLFinal message but received unexpected message")
+	return nil, fmt.Errorf("expected AuthenticationSASLFinal message but received unexpected message %T", msg)
 }
 
 type scramClient struct {
diff --git a/pgconn/config.go b/pgconn/config.go
index bfec11d4..e4a25cb8 100644
--- a/pgconn/config.go
+++ b/pgconn/config.go
@@ -99,10 +99,29 @@ type FallbackConfig struct {
 	TLSConfig *tls.Config // nil disables TLS
 }
 
+// isAbsolutePath checks if the provided value is an absolute path either
+// beginning with a forward slash (as on Linux-based systems) or with a capital
+// letter A-Z followed by a colon and a backslash, e.g., "C:\", (as on Windows).
+func isAbsolutePath(path string) bool {
+	isWindowsPath := func(p string) bool {
+		if len(p) < 3 {
+			return false
+		}
+		drive := p[0]
+		colon := p[1]
+		backslash := p[2]
+		if drive >= 'A' && drive <= 'Z' && colon == ':' && backslash == '\\' {
+			return true
+		}
+		return false
+	}
+	return strings.HasPrefix(path, "/") || isWindowsPath(path)
+}
+
 // NetworkAddress converts a PostgreSQL host and port into network and address suitable for use with
 // net.Dial.
 func NetworkAddress(host string, port uint16) (network, address string) {
-	if strings.HasPrefix(host, "/") {
+	if isAbsolutePath(host) {
 		network = "unix"
 		address = filepath.Join(host, ".s.PGSQL.") + strconv.FormatInt(int64(port), 10)
 	} else {
@@ -341,7 +360,9 @@ func ParseConfig(connString string) (*Config, error) {
 		config.ValidateConnect = ValidateConnectTargetSessionAttrsPrimary
 	case "standby":
 		config.ValidateConnect = ValidateConnectTargetSessionAttrsStandby
-	case "any", "prefer-standby":
+	case "prefer-standby":
+		config.ValidateConnect = ValidateConnectTargetSessionAttrsPreferStandby
+	case "any":
 		// do nothing
 	default:
 		return nil, &parseConfigError{connString: connString, msg: fmt.Sprintf("unknown target_session_attrs value: %v", tsa)}
@@ -772,3 +793,18 @@ func ValidateConnectTargetSessionAttrsPrimary(ctx context.Context, pgConn *PgCon
 
 	return nil
 }
+
+// ValidateConnectTargetSessionAttrsPreferStandby is an ValidateConnectFunc that implements libpq compatible
+// target_session_attrs=prefer-standby.
+func ValidateConnectTargetSessionAttrsPreferStandby(ctx context.Context, pgConn *PgConn) error {
+	result := pgConn.ExecParams(ctx, "select pg_is_in_recovery()", nil, nil, nil, nil).Read()
+	if result.Err != nil {
+		return result.Err
+	}
+
+	if string(result.Rows[0][0]) != "t" {
+		return &NotPreferredError{err: errors.New("server is not in hot standby mode")}
+	}
+
+	return nil
+}
diff --git a/pgconn/config_test.go b/pgconn/config_test.go
index 40db7bc2..b9201d72 100644
--- a/pgconn/config_test.go
+++ b/pgconn/config_test.go
@@ -231,6 +231,18 @@ func TestParseConfig(t *testing.T) {
 				RuntimeParams: map[string]string{},
 			},
 		},
+		{
+			name:       "database url unix domain socket host on windows",
+			connString: "postgres:///foo?host=C:\\tmp",
+			config: &pgconn.Config{
+				User:          osUserName,
+				Host:          "C:\\tmp",
+				Port:          5432,
+				Database:      "foo",
+				TLSConfig:     nil,
+				RuntimeParams: map[string]string{},
+			},
+		},
 		{
 			name:       "database url dbname",
 			connString: "postgres://localhost/?dbname=foo&sslmode=disable",
@@ -600,13 +612,14 @@ func TestParseConfig(t *testing.T) {
 			name:       "target_session_attrs prefer-standby",
 			connString: "postgres://jack:secret@localhost:5432/mydb?sslmode=disable&target_session_attrs=prefer-standby",
 			config: &pgconn.Config{
-				User:          "jack",
-				Password:      "secret",
-				Host:          "localhost",
-				Port:          5432,
-				Database:      "mydb",
-				TLSConfig:     nil,
-				RuntimeParams: map[string]string{},
+				User:            "jack",
+				Password:        "secret",
+				Host:            "localhost",
+				Port:            5432,
+				Database:        "mydb",
+				TLSConfig:       nil,
+				RuntimeParams:   map[string]string{},
+				ValidateConnect: pgconn.ValidateConnectTargetSessionAttrsPreferStandby,
 			},
 		},
 		{
@@ -703,6 +716,55 @@ func TestConfigCopyCanBeUsedToConnect(t *testing.T) {
 	assert.NoError(t, err)
 }
 
+func TestNetworkAddress(t *testing.T) {
+	tests := []struct {
+		name    string
+		host    string
+		wantNet string
+	}{
+		{
+			name:    "Default Unix socket address",
+			host:    "/var/run/postgresql",
+			wantNet: "unix",
+		},
+		{
+			name:    "Windows Unix socket address (standard drive name)",
+			host:    "C:\\tmp",
+			wantNet: "unix",
+		},
+		{
+			name:    "Windows Unix socket address (first drive name)",
+			host:    "A:\\tmp",
+			wantNet: "unix",
+		},
+		{
+			name:    "Windows Unix socket address (last drive name)",
+			host:    "Z:\\tmp",
+			wantNet: "unix",
+		},
+		{
+			name:    "Assume TCP for unknown formats",
+			host:    "a/tmp",
+			wantNet: "tcp",
+		},
+		{
+			name:    "loopback interface",
+			host:    "localhost",
+			wantNet: "tcp",
+		},
+		{
+			name:    "IP address",
+			host:    "127.0.0.1",
+			wantNet: "tcp",
+		},
+	}
+	for i, tt := range tests {
+		gotNet, _ := pgconn.NetworkAddress(tt.host, 5432)
+
+		assert.Equalf(t, tt.wantNet, gotNet, "Test %d (%s)", i, tt.name)
+	}
+}
+
 func assertConfigsEqual(t *testing.T, expected, actual *pgconn.Config, testName string) {
 	if !assert.NotNil(t, expected) {
 		return
diff --git a/pgconn/errors.go b/pgconn/errors.go
index 030f7e0a..4254535e 100644
--- a/pgconn/errors.go
+++ b/pgconn/errors.go
@@ -202,3 +202,20 @@ func redactURL(u *url.URL) string {
 	}
 	return u.String()
 }
+
+type NotPreferredError struct {
+	err         error
+	safeToRetry bool
+}
+
+func (e *NotPreferredError) Error() string {
+	return fmt.Sprintf("standby server not found: %s", e.err.Error())
+}
+
+func (e *NotPreferredError) SafeToRetry() bool {
+	return e.safeToRetry
+}
+
+func (e *NotPreferredError) Unwrap() error {
+	return e.err
+}
diff --git a/pgconn/krb5.go b/pgconn/krb5.go
index a4bca01f..969675fd 100644
--- a/pgconn/krb5.go
+++ b/pgconn/krb5.go
@@ -2,6 +2,7 @@ package pgconn
 
 import (
 	"errors"
+	"fmt"
 
 	"github.com/jackc/pgx/v5/pgproto3"
 )
@@ -87,10 +88,13 @@ func (c *PgConn) rxGSSContinue() (*pgproto3.AuthenticationGSSContinue, error) {
 	if err != nil {
 		return nil, err
 	}
-	gssContinue, ok := msg.(*pgproto3.AuthenticationGSSContinue)
-	if ok {
-		return gssContinue, nil
+
+	switch m := msg.(type) {
+	case *pgproto3.AuthenticationGSSContinue:
+		return m, nil
+	case *pgproto3.ErrorResponse:
+		return nil, ErrorResponseToPgError(m)
 	}
 
-	return nil, errors.New("expected AuthenticationGSSContinue message but received unexpected message")
+	return nil, fmt.Errorf("expected AuthenticationGSSContinue message but received unexpected message %T", msg)
 }
diff --git a/pgconn/pgconn.go b/pgconn/pgconn.go
index ab2e2df9..dcd9dc85 100644
--- a/pgconn/pgconn.go
+++ b/pgconn/pgconn.go
@@ -137,9 +137,12 @@ func ConnectConfig(ctx context.Context, config *Config) (pgConn *PgConn, err err
 		return nil, &connectError{config: config, msg: "hostname resolving error", err: errors.New("ip addr wasn't found")}
 	}
 
+	foundBestServer := false
+	var fallbackConfig *FallbackConfig
 	for _, fc := range fallbackConfigs {
-		pgConn, err = connect(ctx, config, fc)
+		pgConn, err = connect(ctx, config, fc, false)
 		if err == nil {
+			foundBestServer = true
 			break
 		} else if pgerr, ok := err.(*PgError); ok {
 			err = &connectError{config: config, msg: "server error", err: pgerr}
@@ -153,6 +156,17 @@ func ConnectConfig(ctx context.Context, config *Config) (pgConn *PgConn, err err
 				pgerr.Code == ERRCODE_INSUFFICIENT_PRIVILEGE {
 				break
 			}
+		} else if cerr, ok := err.(*connectError); ok {
+			if _, ok := cerr.err.(*NotPreferredError); ok {
+				fallbackConfig = fc
+			}
+		}
+	}
+
+	if !foundBestServer && fallbackConfig != nil {
+		pgConn, err = connect(ctx, config, fallbackConfig, true)
+		if pgerr, ok := err.(*PgError); ok {
+			err = &connectError{config: config, msg: "server error", err: pgerr}
 		}
 	}
 
@@ -176,7 +190,7 @@ func expandWithIPs(ctx context.Context, lookupFn LookupFunc, fallbacks []*Fallba
 
 	for _, fb := range fallbacks {
 		// skip resolve for unix sockets
-		if strings.HasPrefix(fb.Host, "/") {
+		if isAbsolutePath(fb.Host) {
 			configs = append(configs, &FallbackConfig{
 				Host:      fb.Host,
 				Port:      fb.Port,
@@ -216,7 +230,8 @@ func expandWithIPs(ctx context.Context, lookupFn LookupFunc, fallbacks []*Fallba
 	return configs, nil
 }
 
-func connect(ctx context.Context, config *Config, fallbackConfig *FallbackConfig) (*PgConn, error) {
+func connect(ctx context.Context, config *Config, fallbackConfig *FallbackConfig,
+	ignoreNotPreferredErr bool) (*PgConn, error) {
 	pgConn := new(PgConn)
 	pgConn.config = config
 	pgConn.cleanupDone = make(chan struct{})
@@ -330,6 +345,9 @@ func connect(ctx context.Context, config *Config, fallbackConfig *FallbackConfig
 
 				err := config.ValidateConnect(ctx, pgConn)
 				if err != nil {
+					if _, ok := err.(*NotPreferredError); ignoreNotPreferredErr && ok {
+						return pgConn, nil
+					}
 					pgConn.conn.Close()
 					return nil, &connectError{config: config, msg: "ValidateConnect failed", err: err}
 				}