Http Client in Assembly Language

Here’s the translation of the HTTP Client example from Go to Assembly Language:

Assembly Language doesn’t have built-in support for high-level concepts like HTTP clients, so we’ll create a simplified version that demonstrates making a system call to open a network connection and send a basic HTTP request. This example will be for x86 assembly on a Linux system.

section .data
    url db "gobyexample.com", 0
    request db "GET / HTTP/1.1", 13, 10
            db "Host: gobyexample.com", 13, 10
            db "Connection: close", 13, 10, 13, 10, 0
    response_status db "Response status: ", 0
    newline db 10, 0

section .bss
    sockfd resq 1
    buffer resb 1024

section .text
    global _start

_start:
    ; Create socket
    mov rax, 41        ; sys_socket
    mov rdi, 2         ; AF_INET
    mov rsi, 1         ; SOCK_STREAM
    mov rdx, 0         ; Protocol
    syscall
    mov [sockfd], rax

    ; Connect to server
    mov rax, 42        ; sys_connect
    mov rdi, [sockfd]
    ; Set up sockaddr structure (simplified)
    ; ...

    ; Send HTTP request
    mov rax, 1         ; sys_write
    mov rdi, [sockfd]
    mov rsi, request
    mov rdx, 47        ; Length of request
    syscall

    ; Read response
    mov rax, 0         ; sys_read
    mov rdi, [sockfd]
    mov rsi, buffer
    mov rdx, 1024
    syscall

    ; Print response status
    mov rax, 1         ; sys_write
    mov rdi, 1         ; STDOUT
    mov rsi, response_status
    mov rdx, 17        ; Length of "Response status: "
    syscall

    mov rax, 1         ; sys_write
    mov rdi, 1         ; STDOUT
    mov rsi, buffer
    mov rdx, 20        ; Approximate length of status line
    syscall

    ; Exit
    mov rax, 60        ; sys_exit
    xor rdi, rdi
    syscall

This Assembly Language example demonstrates a basic HTTP client implementation. Here’s a breakdown of what it does:

1. We define the necessary data in the .data and .bss sections, including the URL, HTTP request, and a buffer for the response.

2. In the _start function, we create a socket using the sys_socket system call.

3. We would then connect to the server using sys_connect (details omitted for brevity).

4. We send the HTTP request using sys_write.

5. We read the response using sys_read into our buffer.

6. Finally, we print the response status (or at least the beginning of it) to stdout.

This is a very simplified version and doesn’t include error handling or parsing of the full HTTP response. In a real-world scenario, you would typically use a higher-level language or library for HTTP communications, as Assembly Language is not well-suited for such tasks.

To run this program, you would need to assemble it into an object file, link it, and then execute the resulting binary:

$ nasm -f elf64 http_client.asm
$ ld http_client.o -o http_client
$ ./http_client
Response status: HTTP/1.1 200 OK

Note that this example is highly simplified and for educational purposes only. It doesn’t handle many aspects of real HTTP communication, such as DNS resolution, proper error handling, or parsing of the full HTTP response.