utils-net

Building http services

The net/http package handles most of the implementation details for you, so you can focus on instantiating and configuring a server, creating resources, and handling each client request. In Go, an HTTP server relies on several interacting components: handles, middleware, and a multiplexer.

Handlers

When a client sends a request to an HTTP server, the server needs to figure our what to do with it. The server may need to retrieve various resources or perform an action, depending on what the client requests. You may have a handler that knows how to retrieve an image and another that knows how to retrieve information from a database. In Go, handlers are objects that implement the http.Handler interface. They read client requests and write responses -> example.

Injecting dependencies into Handlers

the http.Handler interface gives you access to the request and response objects. But it's likely you'll require access to additional functionality like a logger, metrics, cache, or database to handle a request. For example, you may want to inject a logger to record request errors or inject a database object to retireve data used to create the response. The easiest way to inject an object into a handler is by using a closure.

dbHandler := func(db *sql.DB) http.Handler {
    return http.HandlerFunc(
        func(w http.ResponseWriter, r *http.Request) {
            err := db.Ping()
            // do something with the database here..
        },
    )
}
http.Handle("/three", dbHandler(db))
// Or injecting dependencies into multiple handlers defined as struct methods
type Handlers struct {
    db *sql.Db 
    log *log.Logger
}
func (h *Handlers) Handler1() http.Handler {
    ...
}

Middleware

Middleware comprises reusable functiions that accept an http.Handler and return an http.Handler. You can use middleware to inspect the request and make decisions baased on its content before passing it along to the next handler. Or you might use the request content to set headers in the response. For example, the middleware could respond to the client with an error if the handler requires authentication and an unauthenticated client. middleware

TFTP Server implementation

Trivial File Transfer Protocol

cd udp/tftp/example
go build tftp.go
sudo ./tftp

In other terminal use a TFTP client

tftp 
connect 127.0.0.1
binary
get file.jpeg

Unix Domain Sockets

Stream based files can manage networks like tcp or udp but with a simple file. Sockets for local interprcess communication that allows bidirectional data exhange between processes running on the same machinel.