code: public synchronized static Server getServer(ServerConfig serverConfig) {
          try {
              Server server = SERVER_MAP.get(Integer.toString(serverConfig.getPort()));
              if (server == null) {
                  // 算下网卡和端口
                  resolveServerConfig(serverConfig);
  
                  ExtensionClass<Server> ext = ExtensionLoaderFactory.getExtensionLoader(Server.class)
                      .getExtensionClass(serverConfig.getProtocol());
                  if (ext == null) {
                      throw ExceptionUtils.buildRuntime("server.protocol", serverConfig.getProtocol(),
                          "Unsupported protocol of server!");
                  }
                  server = ext.getExtInstance();
                  server.init(serverConfig);
                  SERVER_MAP.put(serverConfig.getPort() + "", server);
              }
              return server;
          } catch (SofaRpcRuntimeException e) {
              throw e;
          } catch (Throwable e) {
              throw new SofaRpcRuntimeException(e.getMessage(), e);
          }
      }
docs: 初始化Server实例
  
  @param serverConfig 服务端配置
  @return Server