Forking version works

main.S

@@ -13,16 +13,22 @@
 #define	PORT	20335
 
 .data
-greeting: .ascii "Socket test!\n"
+greeting:
+	.ascii	"Welcome to the minimalistic echo server!\n"
+	.ascii	"It is written in pure assembly, and it don't use the standard library, only raw system calls.\n"
+	.ascii	"\n"
+	.ascii	"To exit, press Ctrl+C, as usual\n"
+	.ascii	"\n"
 .set greeting_len, .-greeting
 
-bye: .ascii "Sockets tested!\n"
-.set bye_len, .-bye
+message: .ascii "Client connected\n"
+.set message_len, .-message
 
 errstr: .ascii "Error happened\n"
 .set errstr_len, .-errstr
 
 s:	.quad	0
+s2:	.quad	0
 
 true_val:		.quad	1
 .set true_val_len, .-true_val
@@ -39,7 +45,7 @@ myaddr:
 .text
 .global _start
 _start:
-	movq $STDERR, %rdi
+	movq $STDOUT, %rdi
 	movq $greeting, %rsi
 	movq $greeting_len, %rdx
 	call write_buf
@@ -60,7 +66,7 @@ _start:
 	movq $true_val, %r10
 	movq $true_val_len, %r8
 	syscall
- 	test %rax, %rax
+	test %rax, %rax
 	jnz error
 
 	movq $__NR_bind, %rax
@@ -68,16 +74,17 @@ _start:
 	movq $myaddr, %rsi
 	movq $myaddr_len, %rdx
 	syscall
- 	test %rax, %rax
+	test %rax, %rax
 	jnz error
 
 	movq $__NR_listen, %rax
 	movq s, %rdi
 	movq $8, %rsi
 	syscall
- 	test %rax, %rax
+	test %rax, %rax
 	jnz error
 
+loop:
 	movq $__NR_accept, %rax
 	movq s, %rdi
 	movq $0, %rsi
@@ -86,34 +93,63 @@ _start:
 	syscall
 	cmp $-1, %rax
 	jz error
+	movq %rax, s2
 
-	test %rax, %rax
-	jz error
-
-	movq %rax, %rdi
-	movq $STDOUT, %rsi
-	call passthru
-
-	movq $STDERR, %rdi
-	movq $bye, %rsi
-	movq $bye_len, %rdx
+	movq $STDOUT, %rdi
+	movq $message, %rsi
+	movq $message_len, %rdx
 	call write_buf
 
+	movq $__NR_fork, %rax
+	syscall /* fork! */
+	cmp $-1, %rax
+	jz error
+	test %rax, %rax
+	jz child
+/* we're in the parent if we reach this line */
+
+	movq $__NR_close, %rax
+	movq s2, %rdi
+	syscall
+	test %rax, %rax
+	jnz error
+	jmp loop
+
 exit:
 	movq $__NR_close, %rax
 	movq s, %rdi
 	syscall
+	test %rax, %rax
+	jnz error
 
-_exit:
 	movq $__NR_exit, %rax
 	movq $0, %rdi
 	syscall
-	movq $0, 0
+/* this line is unreachable */
 
 error:
 	movq $__NR_write, %rax
-	movq $STDERR, %rdi
+	movq $STDOUT, %rdi
 	movq $errstr, %rsi
 	movq $errstr_len, %rdx
 	syscall
-	jmp _exit
+
+	movq $__NR_exit, %rax
+	movq $0, %rdi
+	syscall
+/* this line is unreachable */
+
+child:
+/* we're in the child if we reach this line */
+	movq s2, %rdi
+	movq s2, %rsi
+	call passthru
+
+	movq $__NR_close, %rax
+	movq s2, %rdi
+	syscall
+
+	movq $__NR_exit, %rax
+	movq $0, %rdi
+	syscall
+/* this line is unreachable */