Userspace: Implement the most basic http server

This server just responds with static http "hello world" to every
incoming request

userspace/CMakeLists.txt

@@ -7,6 +7,7 @@ set(USERSPACE_PROJECTS
 	dhcp-client
 	echo
 	getopt
+	http-server
 	id
 	image
 	init

userspace/http-server/CMakeLists.txt

@@ -0,0 +1,9 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(http-server ${SOURCES})
+banan_link_library(http-server ban)
+banan_link_library(http-server libc)
+
+install(TARGETS http-server)

userspace/http-server/main.cpp

@@ -0,0 +1,110 @@
+#include <BAN/Vector.h>
+
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/select.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+int main()
+{
+	int socket = ::socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+	if (socket == -1)
+	{
+		perror("socket");
+		return 1;
+	}
+
+	sockaddr_in addr;
+	addr.sin_family = AF_INET;
+	addr.sin_port = htons(8080);
+	addr.sin_addr.s_addr = INADDR_ANY;
+	if (bind(socket, (sockaddr*)&addr, sizeof(addr)) == -1)
+	{
+		perror("bind");
+		return 1;
+	}
+
+	if (listen(socket, SOMAXCONN) == -1)
+	{
+		perror("listen");
+		return 1;
+	}
+
+	printf("server started\n");
+
+	BAN::Vector<int> clients;
+
+	char buffer[1024];
+	while (true)
+	{
+		int max_sock = socket;
+
+		fd_set fds;
+		FD_ZERO(&fds);
+		FD_SET(socket, &fds);
+		for (int client : clients)
+		{
+			FD_SET(client, &fds);
+			max_sock = BAN::Math::max(client, max_sock);
+		}
+
+		if (select(max_sock + 1, &fds, nullptr, nullptr, nullptr) == -1)
+		{
+			perror("select");
+			break;
+		}
+
+		if (FD_ISSET(socket, &fds))
+		{
+			int client = accept(socket, nullptr, nullptr);
+			if (client == -1)
+			{
+				perror("accept");
+				continue;
+			}
+
+			printf("client %d connected\n", client);
+
+			MUST(clients.push_back(client));
+		}
+
+		for (size_t i = 0; i < clients.size();)
+		{
+			if (!FD_ISSET(clients[i], &fds))
+			{
+				i++;
+				continue;
+			}
+
+			ssize_t nrecv = recv(clients[i], buffer, sizeof(buffer), 0);
+			if (nrecv < 0)
+				perror("recv");
+			if (nrecv <= 0)
+			{
+				printf("%d disconnected\n", clients[i]);
+				close(clients[i]);
+				clients.remove(i);
+				continue;
+			}
+
+			write(STDOUT_FILENO, buffer, nrecv);
+
+			strcpy(buffer, "HTTP/1.1 200 OK\r\nContent-Length: 13\r\nConnection: close\r\n\r\nHello, world!");
+			ssize_t nsend = send(clients[i], buffer, strlen(buffer), 0);
+			if (nsend < 0)
+				perror("send");
+			if (nsend <= 0)
+			{
+				printf("%d disconnected\n", clients[i]);
+				close(clients[i]);
+				clients.remove(i);
+				continue;
+			}
+
+			i++;
+		}
+	}
+}