# Gateway

<!-- Version variant: gateway_5; default: [/samples/gateway/index.md](/samples/gateway/index.md) -->



## Code walk-through

This sample demonstrates how logically different sites (such as a headquarters and a remote site) can communicate using the NServiceBus Gateway feature.


## Headquarters.Shared

A shared class library for common code, including message definitions.

## Headquarters

The central endpoint of the Sample.


### Gateway configuration

 * Maps the site key `RemoteSite` to `http://localhost:25899/RemoteSite`
 * Receives incoming messages on `http://localhost:25899/Headquarters/`

<!-- snippet: HeadquartersGatewayConfig -->

```cs
var gatewayConfig = endpointConfiguration.Gateway(new NonDurableDeduplicationConfiguration());
gatewayConfig.AddReceiveChannel("http://localhost:25899/Headquarters/");
gatewayConfig.AddSite("RemoteSite", "http://localhost:25899/RemoteSite/");
```

<!-- endsnippet -->


## AcknowledgedHandler

Handles `PriceUpdateAcknowledged` from `RemoteSite`.

<!-- snippet: AcknowledgedHandler -->

```cs
public class AcknowledgedHandler(ILogger<AcknowledgedHandler> logger) : IHandleMessages<PriceUpdateAcknowledged>
{
    public Task Handle(PriceUpdateAcknowledged message, IMessageHandlerContext context)
    {
        logger.LogInformation("Price update received by: {BranchOffice}", message.BranchOffice);
        return Task.CompletedTask;
    }
}
```

<!-- endsnippet -->


## UpdatePriceHandler

Handles `UpdatePrice` from `WebClient`.

<!-- snippet: UpdatePriceHandler -->

```cs
public class UpdatePriceHandler(ILogger<UpdatePriceHandler> logger) : IHandleMessages<UpdatePrice>
{
    public Task Handle(UpdatePrice message, IMessageHandlerContext context)
    {
        logger.LogInformation("Price update received from the webclient, going to push to RemoteSite");
        string[] siteKeys =
        [
            "RemoteSite"
        ];
        var priceUpdated = new PriceUpdated
        {
            ProductId = message.ProductId,
            NewPrice = message.NewPrice,
            ValidFrom = message.ValidFrom,
        };
        return context.SendToSites(siteKeys, priceUpdated);
    }
}
```

<!-- endsnippet -->


## RemoteSite


### Gateway configuration

Receives incoming messages on `http://localhost:25899/RemoteSite/`

<!-- snippet: RemoteSiteGatewayConfig -->

```cs
var gatewayConfig = endpointConfiguration.Gateway(new NonDurableDeduplicationConfiguration());
gatewayConfig.AddReceiveChannel("http://localhost:25899/RemoteSite/");
```

<!-- endsnippet -->


### PriceUpdatedHandler
   
<!-- snippet: PriceUpdatedHandler -->

```cs
public class PriceUpdatedHandler(ILogger<PriceUpdatedHandler> logger) : IHandleMessages<PriceUpdated>
{
    public Task Handle(PriceUpdated message, IMessageHandlerContext context)
    {
        var header = context.MessageHeaders[Headers.OriginatingSite];
        logger.LogInformation("Price update for: {ProductId} received. Reply over channel: {Channel}", message.ProductId, header);

        var updateAcknowledged = new PriceUpdateAcknowledged
        {
            BranchOffice = "RemoteSite"
        };
        return context.Reply(updateAcknowledged);
    }
}
```

<!-- endsnippet -->


## WebClient

This project represents an external integration point. It sends an `UpdatePrice` message to the channel `http://localhost:25899/Headquarters/`.

<!-- snippet: SendUpdatePrice -->

```html
var message = "<?xml version=\"1.0\" ?><Messages xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\"><UpdatePrice><ProductId>23</ProductId></UpdatePrice></Messages>";
var md5 = b64_md5(message) + "==";
var clientId = Math.uuid() + "\\123456";

$.ajax({
    url: $('#gatewayaddress').val(),
    data: {
        Message: message,
        "NServiceBus.CallType": "SingleCallSubmit",
        "NServiceBus.AutoAck": "true",
        "Content-MD5": md5,
        "NServiceBus.Id": clientId,
        "NServiceBus.EnclosedMessageTypes": "Shared.UpdatePrice, Shared"
    },
    dataType: 'jsonp',
    success: function (data) {
        if (data.status != "OK") {
            alert("Failed to submit the request to the gateway");
            return;
        }
        alert("Success - Check the output of the headquarters server process");
    },
    error: function (http, status) {
        alert("Failed submit: " + status);
    }
});
```

<!-- endsnippet -->