我正在尝试创建一个iOS客户端，通过设备的蜂窝通信将数据发送到UDP套接字上的服务器。
在Does IOS support simultaneous wifi and 3g/4g connections? 链接到iOS Multipath BSD Sockets Test之后，我尝试在Swift 3中实施解决方案，即枚举设备中的网络接口，识别Cellular接口（如Swift - Get device's IP Address中所述） ），创建一个UDP套接字并将其绑定到从接口检索到的 sockaddr 。
在Swift中实现套接字编程是通过以下Socket Programming in Swift: Part 1 - getaddrinfo和以下帖子中的示例完成的。
不幸的是，当我尝试在套接字上发送数据时，我收到操作不允许，所以我尝试创建套接字并将其绑定到来自 getaddrinfo 的数据在指定的港口（5555）。
那也没有做到这一点。 有趣的是，在尝试理解错误的同时，我为这两种方法创建了一个测试应用程序，当测试连续1000次创建 - >绑定 - >发送 - >关闭时，实际上大约有3-5次尝试< strong>执行在任何一种方法上都没有错误地发送数据。
毋庸置疑，这是在真实的iPhone上测试的。
很遗憾，我对此有任何建议。
在静态“SocketManager”类中实现的代码（编辑：固定的sockaddr分配大小）
// Return IP address String, port String & sockaddr of WWAN interface (pdp_ip0), or `nil`
public static func getInterface() -> (String?, String?, UnsafeMutablePointer<sockaddr>?) {
var host : String?
var service : String?
// Get list of all interfaces on the local machine:
var ifaddr : UnsafeMutablePointer<ifaddrs>?
var clt : UnsafeMutablePointer<sockaddr>?
guard getifaddrs(&ifaddr) == 0 else {
return (nil, nil, clt)
}
guard let firstAddr = ifaddr else {
return (nil, nil, clt)
}
// For each interface ...
for ifptr in sequence(first: firstAddr, next: { $0.pointee.ifa_next }) {
let interface = ifptr.pointee
let flags = Int32(ifptr.pointee.ifa_flags)
/// Check for running IPv4 interfaces. Skip the loopback interface.
if (flags & (IFF_UP|IFF_RUNNING|IFF_LOOPBACK)) == (IFF_UP|IFF_RUNNING) {
let addrFamily = interface.ifa_addr.pointee.sa_family
if addrFamily == UInt8(AF_INET) { //Interested in IPv4 for in particular case
// Check interface name:
let name = String(cString: interface.ifa_name)
print("interface name: \(name)")
if name.hasPrefix("pdp_ip") { //cellular interface
// Convert interface address to a human readable string:
let ifa_addr_Value = interface.ifa_addr.pointee
clt = UnsafeMutablePointer<sockaddr>.allocate(capacity: 1)
clt?.initialize(to: ifa_addr_Value, count: 1)
var hostnameBuffer = [CChar](repeating: 0, count: Int(NI_MAXHOST))
var serviceBuffer = [CChar](repeating: 0, count: Int(NI_MAXSERV))
getnameinfo(interface.ifa_addr, socklen_t(ifa_addr_Value.sa_len),
&hostnameBuffer, socklen_t(hostnameBuffer.count),
&serviceBuffer,
socklen_t(serviceBuffer.count),
NI_NUMERICHOST | NI_NUMERICSERV)
host = String(cString: hostnameBuffer)
if let host = host {
print("found host \(String(describing: host))")
}
service = String(cString: serviceBuffer)
if let service = service {
print("found service \(String(describing: service))")
}
break;
}
}
}
}
freeifaddrs(ifaddr)
return (host, service, clt)
}
public static func bindSocket(ip: String, port : String, clt : UnsafeMutablePointer<sockaddr>, useCltAddr : Bool = false) -> Int32 {
print("binding socket for IP: \(ip):\(port) withCltAddr=\(useCltAddr)")
var hints = addrinfo(ai_flags: 0,
ai_family: AF_INET,
ai_socktype: SOCK_DGRAM,
ai_protocol: IPPROTO_UDP,
ai_addrlen: 0,
ai_canonname: nil,
ai_addr: nil,
ai_next: nil)
var connectionInfo : UnsafeMutablePointer<addrinfo>? = nil
let status = getaddrinfo(
ip,
port,
&hints,
&connectionInfo)
if status != 0 {
var strError: String
if status == EAI_SYSTEM {
strError = String(validatingUTF8: strerror(errno)) ?? "Unknown error code"
} else {
strError = String(validatingUTF8: gai_strerror(status)) ?? "Unknown error code"
}
print(strError)
return -1
}
let socketDescriptor = useCltAddr ? socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP) : socket(connectionInfo!.pointee.ai_family, connectionInfo!.pointee.ai_socktype, connectionInfo!.pointee.ai_protocol)
if socketDescriptor == -1 {
let strError = String(utf8String: strerror(errno)) ?? "Unknown error code"
let message = "Socket creation error \(errno) (\(strError))"
freeaddrinfo(connectionInfo)
print(message)
return -1
}
let res = useCltAddr ? bind(socketDescriptor, clt, socklen_t(clt.pointee.sa_len)) : bind(socketDescriptor, connectionInfo?.pointee.ai_addr, socklen_t((connectionInfo?.pointee.ai_addrlen)!))
if res != 0 {
let strError = String(utf8String: strerror(errno)) ?? "Unknown error code"
let message = "Socket bind error \(errno) (\(strError))"
freeaddrinfo(connectionInfo)
close(socketDescriptor)
print(message)
return -1
}
freeaddrinfo(connectionInfo)
print("returned socket descriptor \(socketDescriptor)")
return socketDescriptor
}
//returns 0 for failure, 1 for success
public static func sendData(toIP: String, onPort : String, withSocketDescriptor : Int32, data : Data) -> Int{
print("sendData called for targetIP: \(toIP):\(onPort) with socket descriptor: \(withSocketDescriptor)")
var target = UnsafeMutablePointer<sockaddr_in>.allocate(capacity: MemoryLayout<sockaddr_in>.size)
target.pointee.sin_family = sa_family_t(AF_INET)
target.pointee.sin_addr.s_addr = inet_addr(toIP)
target.pointee.sin_port = in_port_t(onPort)!
var res = 0
data.withUnsafeBytes { (u8Ptr: UnsafePointer<UInt8>) in
let rawPtr = UnsafeRawPointer(u8Ptr)
withUnsafeMutablePointer(to: &target) {
$0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
let bytesSent = sendto(withSocketDescriptor, rawPtr, data.count, 0, $0, socklen_t(MemoryLayout.size(ofValue: target)))
if bytesSent > 0 {
print(" Sent \(bytesSent) bytes ")
res = 1
}
if bytesSent == -1 {
let strError = String(utf8String: strerror(errno)) ?? "Unknown error code"
let message = "Socket sendto error \(errno) (\(strError))"
print(message)
}
}
}
}
return res
}
public static func closeSocket(socketDescriptor : Int32, clt : UnsafeMutablePointer<sockaddr>) {
print("closing socket descriptor \(socketDescriptor)")
close(socketDescriptor)
clt.deinitialize()
clt.deallocate(capacity: 1)
}
在ViewController上：
override func viewDidLoad() {
super.viewDidLoad()
var i = 0
for _ in 0..<1000 {
i += connectSendClose(withDescriptor: false) // change withDescriptor to switch socket create/bind method
}
print("Sent \(i) packets")
}
private func connectSendClose(withDescriptor : Bool) -> Int {
let interface = SocketManager.getInterface()
guard let ip = interface.0 else {
print("no relevant interface")
return 0
}
guard let clt = interface.2 else {
print("no addr")
return 0
}
let socketDescriptor = SocketManager.bindSocket(ip: ip, port: "5555", clt: clt, useCltAddr: withDescriptor)
if socketDescriptor == -1 {
print("faild to configure socket")
return 0
}
let serverIP = "59.122.442.9" //dummy IP, test was preformed on actual server
let serverPort = "10025" //dummy port, test was preformed on actual server
let input = 42.13
var value = input
let data = withUnsafePointer(to: &value) {
Data(bytes: UnsafePointer($0), count: MemoryLayout.size(ofValue: input))
}
let res = SocketManager.sendData(toIP: serverIP, onPort: serverPort, withSocketDescriptor: socketDescriptor, data: data)
SocketManager.closeSocket(socketDescriptor: socketDescriptor, clt: clt)
return res
}
答案 0 :(得分：1)
编辑：修复目标sockadd_in创建时的网络字节顺序错误。
好的，发现了问题：
首先，正如Martin所说，我错过了使用UnsafeMutablePointer分配，因为我将capacity/count参数作为字节。
当我在sockaddr_in函数（sendData而不是var target = UnsafeMutablePointer<sockaddr_in>.allocate(capacity: MemoryLayout<sockaddr_in>.size）中为服务器详细信息分配var target = UnsafeMutablePointer<sockaddr_in>.allocate(capacity: 1时，也完成了此操作。
在解决这个问题之后，我开始获得更好的结果（通过1000个传输中的大约16个），但显然这还不够。
我找到Send a message using UDP in Swift 3，并决定将sockaddr_in更改为var target = sockaddr_in(sin_len: __uint8_t(MemoryLayout<sockaddr_in>.size), sin_family: sa_family_t(AF_INET), sin_port: in_port_t(onPort)!, sin_addr: in_addr(s_addr: inet_addr(toIP)), sin_zero: (0,0,0,0, 0,0,0,0))，一切正常。
我仍然感到困惑的是，为什么在这个结构中使用Unsafe Memory不起作用。
另一件事：我将此代码移回我的实际App，尝试通过addrinfo将套接字绑定到我自己的getaddrinfo，并且无法分配请求的地址，使用我从枚举接口获得的那个工作，但我收到很多没有缓冲区空间错误（另一个研究的东西:)。
在测试代码中，两种绑定方法（枚举＆amp; getaddrinfo）都可以正常工作。
修正sendData功能：
public static func sendData(toIP: String, onPort : String, withSocketDescriptor : Int32, data : Data) -> Int{
print("sendData called for targetIP: \(toIP):\(onPort) with socket descriptor: \(withSocketDescriptor)")
var target = sockaddr_in(sin_len: __uint8_t(MemoryLayout<sockaddr_in>.size), sin_family: sa_family_t(AF_INET), sin_port: in_port_t(bigEndian: onPort)!, sin_addr: in_addr(s_addr: inet_addr(toIP)), sin_zero: (0,0,0,0, 0,0,0,0))
var res = 0
data.withUnsafeBytes { (u8Ptr: UnsafePointer<UInt8>) in
let rawPtr = UnsafeRawPointer(u8Ptr)
withUnsafeMutablePointer(to: &target) {
$0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
let bytesSent = sendto(withSocketDescriptor, rawPtr, data.count, 0, $0, socklen_t(MemoryLayout.size(ofValue: target)))
if bytesSent > 0 {
print(" Sent \(bytesSent) bytes ")
res = 1
}
if bytesSent == -1 {
let strError = String(utf8String: strerror(errno)) ?? "Unknown error code"
let message = "Socket sendto error \(errno) (\(strError))"
print(message)
}
}
}
}
return res
}