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Writing a Network Server in Go: From TCP to HTTP in One Evening

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Why Go is the Ideal Language for Network Programming?

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If you've ever written a network server in Python (especially using socket or asyncio), you know how quickly code can turn into a maze of callbacks and event loops. Go (Golang) solves this problem at the architectural level: goroutines and channels make asynchronous network work as simple as writing sequential code.

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In this article, we'll explore network programming in Go in practice. You'll learn how to build a full-fledged TCP chat in 15 minutes, send a UDP packet, and launch an HTTP server with routing. All examples are working and can be copied and run.

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Basics: The net Package and Its Superpower

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In Go, all the network magic lives in the standard net package. It provides a unified interface for working with TCP, UDP, Unix sockets, and even SSL/TLS. The main feature is that the Listen, Dial, and Accept functions work synchronously but don't block the entire program because each goroutine is lightweight.

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Let's get straight to the point.

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TCP Server: A Chat in 10 Lines

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Let's create a simple echo server that accepts connections and sends back what it received. This is a classic of network programming in Go.

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package main\n\nimport (\n    "bufio"\n    "fmt"\n    "net"\n)\n\nfunc handleConnection(conn net.Conn) {\n    defer conn.Close()\n    scanner := bufio.NewScanner(conn)\n    for scanner.Scan() {\n        message := scanner.Text()\n        fmt.Printf("Received: %s\\n", message)\n        conn.Write([]byte("Echo: " + message + "\\n"))\n    }\n}\n\nfunc main() {\n    listener, _ := net.Listen("tcp", ":8080")\n    fmt.Println("TCP server started on :8080")\n    for {\n        conn, _ := listener.Accept()\n        go handleConnection(conn) // each goroutine is a separate client\n    }\n}
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What's happening here?

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  • net.Listen("tcp", ":8080") — creates a TCP listener on port 8080.
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  • The infinite for loop accepts new connections via Accept().
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  • Each connection is handled in a separate goroutine go handleConnection().
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  • Inside the function, we read lines using bufio.Scanner and send a response.
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Run this code, open a terminal, and connect via nc localhost 8080 (or Putty). Any message will be returned with the prefix "Echo:". Surprisingly, this is already a full-fledged network server capable of serving thousands of clients without a single callback.

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UDP: Fast Delivery Without Guarantees

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If TCP is like a phone call (established a connection — we talk), then UDP is like postcards: sent and forgotten. Go makes working with UDP just as simple.

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UDP Client and Server

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// Server\npackage main\n\nimport (\n    "fmt"\n    "net"\n)\n\nfunc main() {\n    addr, _ := net.ResolveUDPAddr("udp", ":8081")\n    conn, _ := net.ListenUDP("udp", addr)\n    defer conn.Close()\n\n    buffer := make([]byte, 1024)\n    for {\n        n, clientAddr, _ := conn.ReadFromUDP(buffer)\n        message := string(buffer[:n])\n        fmt.Printf("Received from %s: %s\\n", clientAddr, message)\n        conn.WriteToUDP([]byte("Acknowledged: "+message+"\\n"), clientAddr)\n    }\n}\n\n// Client\n// In a separate file or goroutine:\nconn, _ := net.Dial("udp", "localhost:8081")\ndefer conn.Close()\nconn.Write([]byte("Hello, UDP!"))\nbuffer := make([]byte, 1024)\nn, _ := conn.Read(buffer)\nfmt.Println(string(buffer[:n]))
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Key difference from TCP:

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