impl connection recovery

e2e/harness_test.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"bytes"
 	"encoding/binary"
+	"encoding/json"
 	"fmt"
 	"io"
 	"net"
@@ -61,14 +62,33 @@ func freePort(t *testing.T) int {
 // startHub launches the Java hub on the given port and blocks until it accepts
 // connections. The process is killed on test cleanup.
 func startHub(t *testing.T, port int, psk string) {
+	t.Helper()
+	startHubCfg(t, port, psk, nil)
+}
+
+// startHubCfg is startHub with extra config keys merged over the defaults, for
+// tests that need to tune a hub-side knob.
+func startHubCfg(t *testing.T, port int, psk string, extra map[string]any) {
 	t.Helper()
 	install := filepath.Join(repoRoot(), "server", "build", "install", "redapricot-server")
 	if _, err := os.Stat(install); err != nil {
 		t.Fatalf("hub not built at %s (run scripts/build.sh first): %v", install, err)
 	}
-	cfg := fmt.Sprintf(`{"listen":"127.0.0.1:%d","psk":%q,"timestampWindowMs":30000,"pendingTimeoutMs":5000}`, port, psk)
+	settings := map[string]any{
+		"listen":            fmt.Sprintf("127.0.0.1:%d", port),
+		"psk":               psk,
+		"timestampWindowMs": 30000,
+		"pendingTimeoutMs":  5000,
+	}
+	for k, v := range extra {
+		settings[k] = v
+	}
+	cfg, err := json.Marshal(settings)
+	if err != nil {
+		t.Fatal(err)
+	}
 	cfgPath := filepath.Join(t.TempDir(), "hub.json")
-	if err := os.WriteFile(cfgPath, []byte(cfg), 0o644); err != nil {
+	if err := os.WriteFile(cfgPath, cfg, 0o644); err != nil {
 		t.Fatal(err)
 	}