Fix #1481 (with content provider)

httplib.h

@@ -8547,7 +8547,20 @@ inline void ssl_delete(std::mutex &ctx_mutex, SSL *ssl,
   // the remote has closed the network connection
   // Note that it is not always possible to avoid SIGPIPE, this is merely a
   // best-efforts.
-  if (shutdown_gracefully) { SSL_shutdown(ssl); }
+  if (shutdown_gracefully) {
+    auto is_peer_could_be_closed = false;
+    {
+      char buf[1];
+      if (SSL_peek(ssl, buf, 1) == 0 &&
+          SSL_get_error(ssl, 0) == SSL_ERROR_ZERO_RETURN) {
+        is_peer_could_be_closed = true;
+      }
+    }
+
+    if (!is_peer_could_be_closed) {
+      SSL_shutdown(ssl);
+    }
+  }
 
   std::lock_guard<std::mutex> guard(ctx_mutex);
   SSL_free(ssl);

test/test.cc

@@ -4996,6 +4996,60 @@ TEST(KeepAliveTest, SSLClientReconnection) {
   ASSERT_TRUE(result);
   EXPECT_EQ(StatusCode::OK_200, result->status);
 }
+
+TEST(KeepAliveTest, SSLClientReconnectionPost) {
+  SSLServer svr(SERVER_CERT_FILE, SERVER_PRIVATE_KEY_FILE);
+  ASSERT_TRUE(svr.is_valid());
+  svr.set_keep_alive_timeout(1);
+  std::string content = "reconnect";
+
+  svr.Post("/hi", [](const httplib::Request &, httplib::Response &res) {
+    res.set_content("Hello World!", "text/plain");
+  });
+
+  auto f = std::async(std::launch::async, [&svr] { svr.listen(HOST, PORT); });
+  std::this_thread::sleep_for(std::chrono::milliseconds(200));
+
+  SSLClient cli(HOST, PORT);
+  cli.enable_server_certificate_verification(false);
+  cli.set_keep_alive(true);
+
+  auto result = cli.Post(
+      "/hi", content.size(),
+      [&content](size_t offset, size_t length, DataSink &sink) {
+        sink.write(content.c_str(), content.size());
+        return true;
+      },
+      "text/plain");
+  ASSERT_TRUE(result);
+  EXPECT_EQ(200, result->status);
+
+  std::this_thread::sleep_for(std::chrono::seconds(2));
+
+  // Recoonect
+  result = cli.Post(
+      "/hi", content.size(),
+      [&content](size_t offset, size_t length, DataSink &sink) {
+        sink.write(content.c_str(), content.size());
+        return true;
+      },
+      "text/plain");
+  ASSERT_TRUE(result);
+  EXPECT_EQ(200, result->status);
+
+  result = cli.Post(
+      "/hi", content.size(),
+      [&content](size_t offset, size_t length, DataSink &sink) {
+        sink.write(content.c_str(), content.size());
+        return true;
+      },
+      "text/plain");
+  ASSERT_TRUE(result);
+  EXPECT_EQ(200, result->status);
+
+  svr.stop();
+  f.wait();
+}
 #endif
 
 TEST(ClientProblemDetectionTest, ContentProvider) {