socket connection in assembly

# Just a little bit of code to prove to myself that I could actually write in assembly
# To run this, do:
# as code.s -o code.o ; ld code.o -o code ; ./code
# If you want to debug, run it with strace: strace ./code
# Setup a netcat listener on port 31337

# How to do a syscall: http://cs.lmu.edu/~ray/notes/linuxsyscalls/
# List of syscalls: https://filippo.io/linux-syscall-table/

.data

message:
        .asciz "bismillah\r\n"

sockaddr_in:
        .short 2                                        # family (TCP)
        .short 27002                                    # port (31337)
        .long 16777343                                  # addr (127.0.0.1)
        .byte 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00   # zero (buncha zeros!)

.global _start

.text

_start:

        # Update the basepoint
        movq %rsp, %rbp

        # 4 for socket
        # 4 for he socket variable 
        sub $0x8, %rsp

        # Socket syscall
        movq $41, %rax # Socket syscall
        movq $2, %rdi
        movq $1, %rsi
        movq $0, %rdx
        syscall
        mov %rax, -0x4(%rbp) # Record the result

        # Connect syscall
        movq $42, %rax # Connect syscall
        movq -0x4(%rbp), %rdi
        movq $sockaddr_in, %rsi
        movq $16, %rdx
        syscall
#       mov %rax, -0x8(%rbp) # Record the result

        # Write a message
        movq $1, %rax # Write Syscall
        movq -0x4(%rbp), %rdi
        movq $message, %rsi
        movq $12, %rdx # Length of message
        syscall

        # Need to exit the program, exit(0) 
        movq $60, %rax # Exit syscall
        movq $0, %rdi # exit(0)
        syscall