diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
new file mode 100644
index 000000000..39bbd2681
--- /dev/null
+++ b/.devcontainer/devcontainer.json
@@ -0,0 +1,4 @@
+{
+  "image": "mcr.microsoft.com/devcontainers/universal:2",
+  "features": {}
+}
diff --git a/include/co/co/thread.h b/include/co/co/thread.h
index 94845e590..b63ad4883 100644
--- a/include/co/co/thread.h
+++ b/include/co/co/thread.h
@@ -95,4 +95,15 @@ class __coapi sync_event {
     DISALLOW_COPY_AND_ASSIGN(sync_event);
 };
 
+inline int set_thread_name(const char *name) {
+#ifdef _WIN32
+    return 0;
+#elif defined(__APPLE__)
+    ::pthread_setname_np(name);
+    return 0;
+#else
+    return ::pthread_setname_np(::pthread_self(), name);
+#endif
+}
+
 } // co
diff --git a/include/co/god.h b/include/co/god.h
index 3873f4c39..bc0978d3d 100644
--- a/include/co/god.h
+++ b/include/co/god.h
@@ -217,7 +217,7 @@ constexpr bool is_scalar() {
     return std::is_scalar<T>::value;
 }
 
-#if defined(__GNUC__) && __GNUC__ < 5
+#if defined(__GNUC__) && __GNUC__ < 5 && !defined(__APPLE__)
 template<typename T>
 constexpr bool is_trivially_copyable() {
     return __has_trivial_copy(T);
diff --git a/include/co/tcp.h b/include/co/tcp.h
index f331cdef5..aa6f6e524 100644
--- a/include/co/tcp.h
+++ b/include/co/tcp.h
@@ -115,10 +115,7 @@ class __coapi Server final {
     uint32 conn_num() const;
 
     /**
-     * start the server
-     *   - The server will loop in a coroutine, and it will not block the calling thread.
-     *   - The user MUST call on_connection() to set a connection callback before start()
-     *     was called.
+     * config the server
      *   - By default, key and ca are NULL, and ssl is disabled.
      *
      * @param ip    server ip, either an ipv4 or ipv6 address.
@@ -127,7 +124,19 @@ class __coapi Server final {
      * @param key   path of ssl private key file.
      * @param ca    path of ssl certificate file.
      */
-    void start(const char* ip, int port, const char* key=0, const char* ca=0);
+    Server &set_config(const char *ip, int port, const char *key = nullptr, const char *ca = nullptr);
+
+    uint16 get_port() const;
+
+    int listen(int end_port = 0);
+
+    /**
+     * start the server
+     *   - The server will loop in a coroutine, and it will not block the calling thread.
+     *   - The user MUST call on_connection() to set a connection callback before start()
+     *     was called.
+     */
+    void start();
 
     /**
      * exit the server gracefully
diff --git a/src/co/co.cc b/src/co/co.cc
index 08aad350a..56b6cd31a 100644
--- a/src/co/co.cc
+++ b/src/co/co.cc
@@ -321,7 +321,12 @@ bool event_impl::wait(uint32 ms) {
                 _wc.pop_front();
                 !x ? (void)(x = w) : co::free(w, sizeof(*w));
             }
-            x ? (void)(x->state = st_wait) : (void)(x = make_waitx(co));
+            if (x) {
+                x->co = co;
+                x->state = st_wait;
+            } else {
+                x = make_waitx(co);
+            }
             co->waitx = x;
             _wc.push_back(x);
         }
diff --git a/src/co/sched.cc b/src/co/sched.cc
index a590fc279..ed9eccbb9 100644
--- a/src/co/sched.cc
+++ b/src/co/sched.cc
@@ -149,6 +149,8 @@ void Sched::loop() {
     co::vector<Coroutine*> ready_tasks(512);
     co::Timer timer;
 
+    co::set_thread_name("Co_Sched");
+
     while (!_x.stopped) {
         int n = _x.epoll->wait(_wait_ms);
         if (_x.stopped) break;
diff --git a/src/log/log.cc b/src/log/log.cc
index 7e58b888d..cc99e5c1f 100644
--- a/src/log/log.cc
+++ b/src/log/log.cc
@@ -636,6 +636,7 @@ void Logger::write_topic_logs(LogFile& f, const char* topic, const char* p, size
 void Logger::thread_fun() {
     bool signaled;
     int64 sec;
+    co::set_thread_name("Co_Logger");
     while (atomic_load(&g_init_done, mo_acquire) != true) _log_event.wait(8);
     while (!_stop) {
         signaled = _log_event.wait(FLG_log_flush_ms);
diff --git a/src/so/http.cc b/src/so/http.cc
index d9af98a84..886af5872 100644
--- a/src/so/http.cc
+++ b/src/so/http.cc
@@ -680,7 +680,9 @@ void ServerImpl::start(const char* ip, int port, const char* key, const char* ca
     atomic_store(&_started, true, mo_relaxed);
     _serv.on_connection(&ServerImpl::on_connection, this);
     _serv.on_exit([this]() { co::del(this); });
-    _serv.start(ip, port, key, ca);
+    int r = _serv.set_config(ip, port, key, ca).listen();
+    CHECK(r == 0);
+    _serv.start();
 }
 
 inline int hex2int(char c) {
diff --git a/src/so/rpc.cc b/src/so/rpc.cc
index 8d23ff50b..bdcacd322 100644
--- a/src/so/rpc.cc
+++ b/src/so/rpc.cc
@@ -70,7 +70,9 @@ class ServerImpl {
         atomic_store(&_started, true, mo_relaxed);
         _tcp_serv.on_connection(&ServerImpl::on_connection, this);
         _tcp_serv.on_exit([this]() { co::del(this); });
-        _tcp_serv.start(ip, port, key, ca);
+        int r = _tcp_serv.set_config(ip, port, key, ca).listen();
+        CHECK(r == 0);
+        _tcp_serv.start();
     }
 
     bool started() const { return _started; }
diff --git a/src/so/tcp.cc b/src/so/tcp.cc
index e67220ade..a2645a4c6 100644
--- a/src/so/tcp.cc
+++ b/src/so/tcp.cc
@@ -185,7 +185,10 @@ class ServerImpl {
         _exit_cb = std::move(cb);
     }
 
-    void start(const char* ip, int port, const char* key, const char* ca);
+    void set_config(const char *ip, int port, const char *key, const char *ca);
+    uint16 get_port() const { return _port; }
+    int listen(int end_port);
+    void start();
     void exit();
     bool started() const { return _started; }
 
@@ -224,7 +227,7 @@ class ServerImpl {
     } _addr;
 };
 
-void ServerImpl::start(const char* ip, int port, const char* key, const char* ca) {
+void ServerImpl::set_config(const char *ip, int port, const char *key, const char *ca) {
     CHECK(_conn_cb != NULL) << "connection callback not set..";
     _ip = (ip && *ip) ? ip : "0.0.0.0";
     _port = (uint16)port;
@@ -244,27 +247,28 @@ void ServerImpl::start(const char* ip, int port, const char* key, const char* ca
         CHECK_EQ(r, 1) << "ssl check private key error: " << ssl::strerror();
 
         _on_sock = std::bind(&ServerImpl::on_ssl_connection, this, std::placeholders::_1);
-        this->ref();
-        atomic_store(&_started, true, mo_relaxed);
-        go(&ServerImpl::loop, this);
     } else {
         _on_sock = std::bind(&ServerImpl::on_tcp_connection, this, std::placeholders::_1);
-        this->ref();
-        atomic_store(&_started, true, mo_relaxed);
-        go(&ServerImpl::loop, this);
     }
 }
 
+void ServerImpl::start() {
+    CHECK(_on_sock && _fd >= 0) << "must set_config and listen";
+    this->ref();
+    atomic_store(&_started, true, mo_relaxed);
+    go(&ServerImpl::loop, this);
+}
+
 void ServerImpl::exit() {
     int status = atomic_cas(&_status, 0, 1);
     if (status == 2) return; // already stopped
 
     if (status == 0) {
-        sleep::ms(1);
-        if (status != 2) go(&ServerImpl::stop, this);
+        co::sleep(1);
+        go(&ServerImpl::stop, this);
     }
 
-    while (_status != 2) sleep::ms(1);
+    while (_status != 2) co::sleep(1);
 }
 
 void ServerImpl::stop() {
@@ -273,39 +277,94 @@ void ServerImpl::stop() {
     c.connect(-1);
 }
 
-/**
- * the server loop 
- *   - It listens on a port and waits for connections. 
- *   - When a connection is accepted, it will start a new coroutine and call 
- *     the connection callback to handle the connection. 
- */
-void ServerImpl::loop() {
-    do {
-        fastring port = str::from(_port);
-        struct addrinfo* info = 0;
-        int r = getaddrinfo(_ip.c_str(), port.c_str(), NULL, &info);
-        CHECK_EQ(r, 0) << "invalid ip address: " << _ip << ':' << _port;
-        CHECK(info != NULL);
+int ServerImpl::listen(int end_port) {
+    int r = EINVAL;
+    if (_fd >= 0) return r;
+    if (end_port < _port) end_port = _port;
 
-        _fd = co::tcp_socket(info->ai_family);
-        CHECK_NE(_fd, (sock_t)-1) << "create socket error: " << co::strerror();
-        co::set_reuseaddr(_fd);
+    auto start_time = now::ms();
+
+    for (uint16 port_num = _port; port_num <= (uint16) end_port;) {
+        fastring port = str::from(port_num);
+        struct addrinfo *info = nullptr;
+        r = ::getaddrinfo(_ip.c_str(), port.c_str(), nullptr, &info);
+        if (r) {
+            ELOG << "getaddrinfo " << _ip << ':' << port << " error: (" << r << ") " << ::gai_strerror(r);
+            break;
+        }
+        CHECK(info);
+
+        bool retry = false;
+
+        sock_t fd = co::tcp_socket(info->ai_family);
+        if (fd < 0) {
+            r = errno;
+            goto end;
+        }
+        co::set_reuseaddr(fd);
 
         // turn off IPV6_V6ONLY
         if (info->ai_family == AF_INET6) {
             int on = 0;
-            co::setsockopt(_fd, IPPROTO_IPV6, IPV6_V6ONLY, &on, sizeof(on));
+            co::setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &on, sizeof(on));
         }
 
-        r = co::bind(_fd, info->ai_addr, (int)info->ai_addrlen);
-        CHECK_EQ(r, 0) << "bind " << _ip << ':' << _port << " failed: " << co::strerror();
+        r = co::bind(fd, info->ai_addr, (int) info->ai_addrlen);
+        if (r < 0) {
+            r = errno;
+            if (r == EADDRNOTAVAIL) {
+                if (now::ms() - start_time <= 20000) {
+                    retry = true;
+                    DLOG << "bind " << _ip << ':' << port << " error: (" << r << ") " << co::strerror(r);
+                    co::sleep(1000);
+                } else {
+                    ELOG << "bind " << _ip << ':' << port << " error: (" << r << ") " << co::strerror(r);
+                }
+            } else if (r == EADDRINUSE && now::ms() - start_time <= 40000) {
+                retry = true;
+                DLOG << "bind " << _ip << ':' << port << " error: (" << r << ") " << co::strerror(r);
+                co::sleep(20);
+                if (++port_num > (uint16) end_port) port_num = _port;
+            } else {
+                ELOG << "bind " << _ip << ':' << port << " error: (" << r << ") " << co::strerror(r);
+            }
+            goto end;
+        }
 
-        r = co::listen(_fd, 64 * 1024);
-        CHECK_EQ(r, 0) << "listen error: " << co::strerror();
+        r = co::listen(fd, 64 * 1024);
+        if (r < 0) {
+            r = errno;
+            if (r == EADDRINUSE && now::ms() - start_time <= 40000) {
+                retry = true;
+                DLOG << "listen " << _ip << ':' << port << " error: (" << r << ") " << co::strerror(r);
+                co::sleep(20);
+                if (++port_num > (uint16) end_port) port_num = _port;
+            } else {
+                ELOG << "listen " << _ip << ':' << port << " error: (" << r << ") " << co::strerror(r);
+            }
+            goto end;
+        }
 
-        freeaddrinfo(info);
-    } while (0);
+        _port = port_num;
+        _fd = fd;
+        fd = -1;
 
+        end:
+        if (fd >= 0) co::close(fd);
+        if (info) ::freeaddrinfo(info);
+        if (!retry) break;
+    }
+
+    return r;
+}
+
+/**
+ * the server loop 
+ *   - It listens on a port and waits for connections. 
+ *   - When a connection is accepted, it will start a new coroutine and call 
+ *     the connection callback to handle the connection. 
+ */
+void ServerImpl::loop() {
     LOG << "server start: " << _ip << ':' << _port;
     while (true) {
         _addrlen = sizeof(_addr);
@@ -395,10 +454,17 @@ uint32 Server::conn_num() const {
     return ((ServerImpl*)_p)->conn_num();
 }
 
-void Server::start(const char* ip, int port, const char* key, const char* ca) {
-    ((ServerImpl*)_p)->start(ip, port, key, ca);
+Server &Server::set_config(const char *ip, int port, const char *key, const char *ca) {
+    ((ServerImpl *) _p)->set_config(ip, port, key, ca);
+    return *this;
 }
 
+uint16 Server::get_port() const { return ((ServerImpl *) _p)->get_port(); }
+
+int Server::listen(int end_port) { return ((ServerImpl *) _p)->listen(end_port); }
+
+void Server::start() { ((ServerImpl *) _p)->start(); }
+
 void Server::exit() {
     ((ServerImpl*)_p)->exit();
 }
diff --git a/src/tasked.cc b/src/tasked.cc
index c7f6bed72..7728ff6b0 100644
--- a/src/tasked.cc
+++ b/src/tasked.cc
@@ -80,6 +80,8 @@ void TaskedImpl::loop() {
     co::Timer timer;
     co::vector<Task> tmp(32);
 
+    co::set_thread_name("Co_Tasked");
+
     while (!_stop) {
         timer.restart();
         {
diff --git a/test/so/echo.cc b/test/so/echo.cc
index 2f71d7ddb..9ff1f8952 100644
--- a/test/so/echo.cc
+++ b/test/so/echo.cc
@@ -77,7 +77,10 @@ int main(int argc, char** argv) {
     flag::parse(argc, argv);
 
     if (FLG_s) {
-        tcp::Server().on_connection(conn_cb).start("0.0.0.0", FLG_p);
+        tcp::Server serv;
+        serv.on_connection(conn_cb).set_config("0.0.0.0", FLG_p);
+        if (serv.listen() != 0) return 1;
+        serv.start();
         while (true) sleep::sec(1024);
     } else {
         g_count = (Count*) co::zalloc(sizeof(Count) * FLG_c);
diff --git a/test/so/ssl.cc b/test/so/ssl.cc
index 4d874101e..43e1b55f5 100644
--- a/test/so/ssl.cc
+++ b/test/so/ssl.cc
@@ -118,11 +118,15 @@ int main(int argc, char** argv) {
     CHECK(!FLG_ca.empty()) << "ssl certificate file not set..";
 
     if (FLG_t == 0) {
-        serv.start(FLG_ip.c_str(), FLG_port, FLG_key.c_str(), FLG_ca.c_str());
+        serv.set_config(FLG_ip.c_str(), FLG_port, FLG_key.c_str(), FLG_ca.c_str());
+        if (serv.listen() != 0) return 1;
+        serv.start();
         sleep::ms(32);
         go(client_fun);
     } else if (FLG_t == 1) {
-        serv.start(FLG_ip.c_str(), FLG_port, FLG_key.c_str(), FLG_ca.c_str());
+        serv.set_config(FLG_ip.c_str(), FLG_port, FLG_key.c_str(), FLG_ca.c_str());
+        if (serv.listen() != 0) return 1;
+        serv.start();
     } else {
         go(client_fun);
     }
diff --git a/test/so/tcp.cc b/test/so/tcp.cc
index 93e2e457e..a80e14535 100644
--- a/test/so/tcp.cc
+++ b/test/so/tcp.cc
@@ -103,9 +103,15 @@ int main(int argc, char** argv) {
         [](void* p) { delete (tcp::Client*) p; }
     );
 
-    tcp::Server().on_connection(conn_cb).start(
+    tcp::Server serv;
+    serv.on_connection(conn_cb).set_config(
         "0.0.0.0", FLG_port, FLG_key.c_str(), FLG_ca.c_str()
     );
+    if (serv.listen() != 0) {
+        delete gPool;
+        return 1;
+    }
+    serv.start();
 
     sleep::ms(32);
 
diff --git a/test/so/tcp2.cc b/test/so/tcp2.cc
index ffe99bfaa..399b9b679 100644
--- a/test/so/tcp2.cc
+++ b/test/so/tcp2.cc
@@ -117,9 +117,14 @@ int main(int argc, char** argv) {
     );
 
     tcp::Server serv;
-    serv.on_connection(conn_cb).start(
+    serv.on_connection(conn_cb).set_config(
         FLG_ip.c_str(), FLG_port, FLG_key.c_str(), FLG_ca.c_str()
     );
+    if (serv.listen() != 0) {
+        delete gPool;
+        return 1;
+    }
+    serv.start();
     sleep::ms(32);
 
     if (FLG_client_num > 1) {