A micro web server that replies "Hello world!" to every request
The idea is to show the basics steps to create a web server in Swift.
A web server overview:
func startWebServer(){
let socketDescriptor = Darwin.socket(AF_INET, SOCK_STREAM, 0)socket -- creates an endpoint for communication and returns a descriptor.
domain: Communication domain, selects the protocol family, in our case ipv4 (AF_INET). AF_INET6 if we wanted to use ipv6.
type: Specifies semantics of communication. A SOCK_STREAM type provides sequenced, reliable, two-way connection based byte streams.
protocol: The protocol specifies a particular protocol to be used with the socket. Normally only a single protocol exists to support a particular socket type within a given protocol family
Returns -1 if there's an error otherwise the descriptor (a reference).
var noSigPipe: Int32 = 1
setsockopt(socketDescriptor, SOL_SOCKET, SO_NOSIGPIPE, &noSigPipe, socklen_t(MemoryLayout<Int32>.size))setsockopt -- get and set options on sockets
socket: The socket descriptor
level: To manipulate options at the socket level
option_name: The name of our the option, in our case we do not generate SIGPIPE, instead return EPIPE A SIGPIPE is sent to a process if it tried to write to a socket that had been shutdown for writing or isn't connected (anymore).
socklen_t: the option length
let port: in_port_t = 9292
var address = sockaddr_in(
sin_len: UInt8(MemoryLayout<sockaddr_in>.stride),
sin_family: UInt8(AF_INET),
sin_port: port.bigEndian,
sin_addr: in_addr(s_addr: in_addr_t(0)),
sin_zero:(0, 0, 0, 0, 0, 0, 0, 0) // Add some padding, more info at: http://stackoverflow.com/questions/15608707/why-is-zero-padding-needed-in-sockaddr-in#15609050
)
var bindResult: Int32 = -1
bindResult = withUnsafePointer(to: &address) {
bind(socketDescriptor, UnsafePointer<sockaddr>(OpaquePointer($0)), socklen_t(MemoryLayout<sockaddr_in>.size))
}bind -- assigns a name to an unnamed socket.
When a socket is created with socket() it exists in a name space (address family) but has no name assigned. bind() requests that address be assigned to the socket.
if bindResult == -1 {
fatalError(String(cString: UnsafePointer(strerror(errno))))
}
listen(socketDescriptor, SOMAXCONN)listen -- for connections on a socket
The backlog parameter defines the maximum length for the queue of pending connections. If a connection request arrives with the queue full, the client may receive an error with an indication of ECONNREFUSED.
print("Starting HTTP server on port \(port)")
repeat {
var address = sockaddr()
var length: socklen_t = 0
let clientSocket = accept(socketDescriptor, &address, &length)
if clientSocket == -1 {
fatalError(String(cString: UnsafePointer(strerror(errno))))
}accept -- extracts the first connection request on the queue of pending connections,
Creates a new socket with the same properties of socket, and allocates a new file descriptor for the socket.
The argument address is a result parameter that is filled in with the address of the connecting entity, as known to the communications layer.
The address_len is a value-result parameter; it should initially contain the amount of space pointed to by address; on return it will contain the actual length (in bytes) of the address returned.
var characters = ""
var received: UInt8 = 0
repeat {
var buffer = [UInt8](repeatElement(0, count: 1))
recv -- receive a message from a socket
let resp = recv(clientSocket, &buffer, Int(buffer.count), 0)
if resp <= 0 {
fatalError(String(cString: UnsafePointer(strerror(errno))))
}
received = buffer.first!
if received > 13 /* Carriage Return on ASCII table */ {
characters.append(Character(UnicodeScalar(received)))
}
} while received != 10 /* New Line on ASCII table */
print("Received -> \(characters)")write -- write output
let message = "HTTP/1.1 200 OK\r\n\r\n Hello World!"
print("Response -> \(message)")
let messageData = ArraySlice(message.utf8)
_ = messageData.withUnsafeBytes {
write(clientSocket, $0.baseAddress, messageData.count)
}
close -- delete a descriptor
close(clientSocket)
} while true
}
startWebServer()