前言

Signalr 即时消息发布到服务器后发现链接老是自动断开，导致无法发送广播
后面百度搜了一下，signalr有个超时的机制

解决办法（js）

//链接到自己的hub
var connection = new signalR.HubConnectionBuilder().withUrl("/SignalR/chatHub").build();
//重连方法
const startSignalRConnection = connection => connection.start()
.then(() => console.info("重连成功！"))
.catch(err =>
// console.error('SignalR Connection Error: ', err)
layer.alert("即时消息链接已断开，请重新刷新页面"));
//启动链接
async function start() {
try {
await connection.start().then(function () {
}).catch(function (err) {
return console.error(err.toString());
});
console.log("connected");
} catch (err) {
console.log(err);
setTimeout(() => start(), 5000);
}
};
start();
//设置超时时间(30分钟超时)
connection.serverTimeoutInMilliseconds = 30 * 60 * 1000;
//超时时间过了之后会自动断开链接
//链接断开，尝试重连
connection.onclose(() => setTimeout(startSignalRConnection(connection), 5000));

只需要在断开的时候重连就行了

后端同样也有链接断开，连接中，链接成功的回调，根据需要选择
一般重连在前端展示就行

//指定重连间隔：0s,0s,10s
HubConnection hubConnection = new HubConnectionBuilder()
.WithUrl(new Uri("http://localhost/chathub"))
.WithAutomaticReconnect(new[] { TimeSpan.Zero, TimeSpan.Zero, TimeSpan.FromSeconds(10) })
.Build();
HubConnectionBuilder hubConnectionBuilder = new HubConnectionBuilder();
//重连
hubConnectionBuilder = (HubConnectionBuilder)hubConnectionBuilder
.WithAutomaticReconnect();
//创建连接对象
hubConnection = hubConnectionBuilder.Build();
//断开连接
hubConnection.Closed += async (exception) =>
{
/ await Task.Delay(0);
};
//重连中
hubConnection.Reconnecting += async (exception) =>
{
await Task.Delay(0);
};
//重连成功
hubConnection.Reconnected += async (exception) =>
{
await Task.Delay(0);
};
//心跳检查
hubConnection.KeepAliveInterval = TimeSpan.FromSeconds(60);

按需求选则前端或后端代码