Implemented a UDPConnection class as a wrapper around a UDP implementation

BitTorrent.xcodeproj/project.pbxproj

@@ -10,6 +10,8 @@
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+		B50B24F71F0A553F00C23E7C /* UDPConnectionTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = B50B24F61F0A553B00C23E7C /* UDPConnectionTests.swift */; };
+		B50B24F91F0A554A00C23E7C /* UDPConnection.swift in Sources */ = {isa = PBXBuildFile; fileRef = B50B24F81F0A554A00C23E7C /* UDPConnection.swift */; };
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@@ -25,6 +27,9 @@
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 		B55317E01F02FE1500909ADF /* URLEncodeTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = B55317DF1F02FE1500909ADF /* URLEncodeTests.swift */; };
+		B556D5AE1F0BA1FD00277B8D /* GCDAsyncUdpSocketStub.swift in Sources */ = {isa = PBXBuildFile; fileRef = B551C9541F0B9D3D004115CB /* GCDAsyncUdpSocketStub.swift */; };
+		B558F4831F0A647D00438BB4 /* InternetProtocol.swift in Sources */ = {isa = PBXBuildFile; fileRef = B558F4821F0A647D00438BB4 /* InternetProtocol.swift */; };
+		B558F4851F0A73D000438BB4 /* InternetProtocolTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = B558F4841F0A73D000438BB4 /* InternetProtocolTests.swift */; };
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@@ -112,6 +117,8 @@
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+		B50B24F61F0A553B00C23E7C /* UDPConnectionTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UDPConnectionTests.swift; sourceTree = "<group>"; };
+		B50B24F81F0A554A00C23E7C /* UDPConnection.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UDPConnection.swift; sourceTree = "<group>"; };
 		B537CF051F03148B0084089B /* HTTPConnectionStub.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; name = HTTPConnectionStub.swift; path = "HTTP Networking/HTTPConnectionStub.swift"; sourceTree = "<group>"; };
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 		B54D0C231CA56A22004343BD /* TorrentMetaInfo.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; name = TorrentMetaInfo.swift; path = Models/TorrentMetaInfo.swift; sourceTree = "<group>"; };
@@ -123,10 +130,13 @@
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+		B551C9541F0B9D3D004115CB /* GCDAsyncUdpSocketStub.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GCDAsyncUdpSocketStub.swift; sourceTree = "<group>"; };
 		B5530DB11F03063300F71CCD /* HTTPConnection.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; name = HTTPConnection.swift; path = "HTTP Networking/HTTPConnection.swift"; sourceTree = "<group>"; };
 		B5530DB41F03063E00F71CCD /* HTTPConnectionTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; name = HTTPConnectionTests.swift; path = "HTTP Networking/HTTPConnectionTests.swift"; sourceTree = "<group>"; };
 		B55317DB1F02FC4D00909ADF /* TorrentHTTPTracker.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; name = TorrentHTTPTracker.swift; path = Tracker/TorrentHTTPTracker.swift; sourceTree = "<group>"; };
 		B55317DF1F02FE1500909ADF /* URLEncodeTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; name = URLEncodeTests.swift; path = "HTTP Networking/URLEncodeTests.swift"; sourceTree = "<group>"; };
+		B558F4821F0A647D00438BB4 /* InternetProtocol.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = InternetProtocol.swift; sourceTree = "<group>"; };
+		B558F4841F0A73D000438BB4 /* InternetProtocolTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = InternetProtocolTests.swift; sourceTree = "<group>"; };
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 		B585AB741C3833450093FA41 /* BitTorrent.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = BitTorrent.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		B585AB771C3833450093FA41 /* BitTorrent.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = BitTorrent.h; sourceTree = "<group>"; };
@@ -204,6 +214,18 @@
 			name = Pods;
 			sourceTree = "<group>";
 		};
+		B50B24F01F0A54C100C23E7C /* UDP Networking */ = {
+			isa = PBXGroup;
+			children = (
+				B558F4821F0A647D00438BB4 /* InternetProtocol.swift */,
+				B558F4841F0A73D000438BB4 /* InternetProtocolTests.swift */,
+				B50B24F81F0A554A00C23E7C /* UDPConnection.swift */,
+				B551C9541F0B9D3D004115CB /* GCDAsyncUdpSocketStub.swift */,
+				B50B24F61F0A553B00C23E7C /* UDPConnectionTests.swift */,
+			);
+			path = "UDP Networking";
+			sourceTree = "<group>";
+		};
 		B54D0C131CA53979004343BD /* Frameworks */ = {
 			isa = PBXGroup;
 			children = (
@@ -306,6 +328,7 @@
 				B54D0C251CA56A25004343BD /* Models */,
 				B54D0C291CA5785F004343BD /* Utilities */,
 				B5E9778F1CAFB2090038EBE7 /* HTTP Networking */,
+				B50B24F01F0A54C100C23E7C /* UDP Networking */,
 				B585AB791C3833450093FA41 /* Info.plist */,
 			);
 			path = BitTorrent;
@@ -712,10 +735,12 @@
 				B5F81E491F0436D600B25C70 /* TorrentPeer.swift in Sources */,
 				B55317DC1F02FC4D00909ADF /* TorrentHTTPTracker.swift in Sources */,
 				B5E977961CAFB46B0038EBE7 /* String+URLEncode.swift in Sources */,
+				B558F4831F0A647D00438BB4 /* InternetProtocol.swift in Sources */,
 				B54D0C7A1CA69FAD004343BD /* TorrentMetaInfo.swift in Sources */,
 				B5F81E4B1F04399800B25C70 /* TorrentTrackerResponse.swift in Sources */,
 				B54D0C7B1CA69FD8004343BD /* Data+sha1.swift in Sources */,
 				B5530DB21F03063300F71CCD /* HTTPConnection.swift in Sources */,
+				B50B24F91F0A554A00C23E7C /* UDPConnection.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -725,11 +750,14 @@
 			files = (
 				B537CF061F03148B0084089B /* HTTPConnectionStub.swift in Sources */,
 				B5BD7FD61F03032400621BC2 /* TorrentHTTPTrackerTests.swift in Sources */,
+				B556D5AE1F0BA1FD00277B8D /* GCDAsyncUdpSocketStub.swift in Sources */,
 				B5530DB51F03063E00F71CCD /* HTTPConnectionTests.swift in Sources */,
 				B56A8A071C83539300426AC8 /* TestHelpers.swift in Sources */,
 				B585AB841C3833450093FA41 /* BitTorrentTests.swift in Sources */,
 				B54D0C271CA56ADB004343BD /* TorrentMetaInfoTests.swift in Sources */,
 				B55317E01F02FE1500909ADF /* URLEncodeTests.swift in Sources */,
+				B558F4851F0A73D000438BB4 /* InternetProtocolTests.swift in Sources */,
+				B50B24F71F0A553F00C23E7C /* UDPConnectionTests.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

BitTorrent/BitTorrent-Bridging-Header.h

@@ -0,0 +1,12 @@
+//
+//  Use this file to import your target's public headers that you would like to expose to Swift.
+//
+
+#import <CommonCrypto/CommonCrypto.h>
+#import "GCDAsyncSocket.h"
+#import "GCDAsyncUdpSocket.h"
+#import "InternetProtocol.h"
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>

BitTorrent/UDP Networking/GCDAsyncUdpSocketStub.swift

@@ -0,0 +1,58 @@
+//
+//  GCDAsyncUdpSocketProtocol.swift
+//  BitTorrent
+//
+//  Created by Ben Davis on 04/07/2017.
+//  Copyright © 2017 Ben Davis. All rights reserved.
+//
+
+import Foundation
+import CocoaAsyncSocket
+
+class GCDAsyncUdpSocketStub: GCDAsyncUdpSocket {
+    
+    weak var _delegate: GCDAsyncUdpSocketDelegate?
+    
+    override func delegate() -> GCDAsyncUdpSocketDelegate? {
+        return _delegate
+    }
+    
+    override func setDelegate(_ delegate: GCDAsyncUdpSocketDelegate?) {
+        _delegate = delegate
+    }
+    
+    var bindToPortCalled = false
+    var bindToPortParameter: UInt16?
+    override func bind(toPort port: UInt16) throws {
+        bindToPortCalled = true
+        bindToPortParameter = port
+    }
+    
+    var beginReceivingCalled = false
+    override func beginReceiving() throws {
+        beginReceivingCalled = true
+    }
+    
+    var _delegateQueue: DispatchQueue?
+    
+    override func delegateQueue() -> DispatchQueue? {
+        return _delegateQueue
+    }
+    
+    override func synchronouslySetDelegateQueue(_ delegateQueue: DispatchQueue?) {
+        _delegateQueue = delegateQueue
+    }
+    
+    var closeCalled = false
+    override func close() {
+        closeCalled = true
+    }
+    
+    var sendCalled = false
+    var sendParameters: (data: Data, host: String, port: UInt16, timeout: TimeInterval, tag: Int)?
+    override func send(_ data: Data, toHost host: String, port: UInt16, withTimeout timeout: TimeInterval, tag: Int) {
+        sendCalled = true
+        sendParameters = (data, host, port, timeout, tag)
+    }
+}
+

BitTorrent/UDP Networking/InternetProtocol.h

@@ -0,0 +1,21 @@
+//
+//  InternetProtocol.h
+//  BitTorrent
+//
+//  Created by Ben Davis on 16/11/2014.
+//  Copyright (c) 2014 Ben Davis. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+@interface InternetProtocol : NSObject
+
++ (NSString *)getIPAddress:(BOOL)preferIPv4;
++ (NSDictionary *)getIPAddresses;
+
++ (NSString*)ipAddressOfHostname:(NSString*)hostName;
+
++ (NSString*)ipAddressFromSockAddrData:(NSData*)data;
++ (uint16_t)portFromSockAddrData:(NSData*)data;
+
+@end

BitTorrent/UDP Networking/InternetProtocol.m

@@ -0,0 +1,105 @@
+//
+//  InternetProtocol.m
+//  BitTorrent
+//
+//  Created by Ben Davis on 16/11/2014.
+//  Copyright (c) 2014 Ben Davis. All rights reserved.
+//
+
+#import "InternetProtocol.h"
+#include <ifaddrs.h>
+#include <arpa/inet.h>
+#include <net/if.h>
+#include <netdb.h>
+
+#define IOS_CELLULAR    @"pdp_ip0"
+#define IOS_WIFI        @"en0"
+#define IP_ADDR_IPv4    @"ipv4"
+#define IP_ADDR_IPv6    @"ipv6"
+
+@implementation InternetProtocol
+
++ (NSString *)getIPAddress:(BOOL)preferIPv4 {
+    NSArray *searchArray = preferIPv4 ?
+    @[ IOS_WIFI @"/" IP_ADDR_IPv4, IOS_WIFI @"/" IP_ADDR_IPv6, IOS_CELLULAR @"/" IP_ADDR_IPv4, IOS_CELLULAR @"/" IP_ADDR_IPv6 ] :
+    @[ IOS_WIFI @"/" IP_ADDR_IPv6, IOS_WIFI @"/" IP_ADDR_IPv4, IOS_CELLULAR @"/" IP_ADDR_IPv6, IOS_CELLULAR @"/" IP_ADDR_IPv4 ] ;
+    
+    NSDictionary *addresses = [self getIPAddresses];
+    NSLog(@"addresses: %@", addresses);
+    
+    __block NSString *address;
+    [searchArray enumerateObjectsUsingBlock:^(NSString *key, NSUInteger idx, BOOL *stop)
+     {
+         address = addresses[key];
+         if(address) *stop = YES;
+     } ];
+    return address ? address : @"0.0.0.0";
+}
+
++ (NSDictionary *)getIPAddresses {
+    NSMutableDictionary *addresses = [NSMutableDictionary dictionaryWithCapacity:8];
+    
+    // retrieve the current interfaces - returns 0 on success
+    struct ifaddrs *interfaces;
+    if(!getifaddrs(&interfaces)) {
+        // Loop through linked list of interfaces
+        struct ifaddrs *interface;
+        for(interface=interfaces; interface; interface=interface->ifa_next) {
+            if(!(interface->ifa_flags & IFF_UP) /* || (interface->ifa_flags & IFF_LOOPBACK) */ ) {
+                continue; // deeply nested code harder to read
+            }
+            const struct sockaddr_in *addr = (const struct sockaddr_in*)interface->ifa_addr;
+            char addrBuf[ MAX(INET_ADDRSTRLEN, INET6_ADDRSTRLEN) ];
+            if(addr && (addr->sin_family==AF_INET || addr->sin_family==AF_INET6)) {
+                NSString *name = [NSString stringWithUTF8String:interface->ifa_name];
+                NSString *type;
+                if(addr->sin_family == AF_INET) {
+                    if(inet_ntop(AF_INET, &addr->sin_addr, addrBuf, INET_ADDRSTRLEN)) {
+                        type = IP_ADDR_IPv4;
+                    }
+                } else {
+                    const struct sockaddr_in6 *addr6 = (const struct sockaddr_in6*)interface->ifa_addr;
+                    if(inet_ntop(AF_INET6, &addr6->sin6_addr, addrBuf, INET6_ADDRSTRLEN)) {
+                        type = IP_ADDR_IPv6;
+                    }
+                }
+                if(type) {
+                    NSString *key = [NSString stringWithFormat:@"%@/%@", name, type];
+                    addresses[key] = [NSString stringWithUTF8String:addrBuf];
+                }
+            }
+        }
+        // Free memory
+        freeifaddrs(interfaces);
+    }
+    return [addresses count] ? addresses : nil;
+}
+
++(NSString *)ipAddressOfHostname:(NSString *)hostName {
+    struct hostent *host_entry = gethostbyname([hostName cStringUsingEncoding:NSASCIIStringEncoding]);
+    char *buff;
+    if (host_entry != NULL) {
+        buff = inet_ntoa(*((struct in_addr *)host_entry->h_addr_list[0]));
+        NSString *ip = [NSString stringWithUTF8String:buff];
+        return ip;
+    } else {
+        return nil;
+    }
+}
+
++ (NSString*)ipAddressFromSockAddrData:(NSData*)data {
+    struct sockaddr_in * socketAddress = (struct sockaddr_in *)data.bytes;
+    struct	in_addr ipAsStruct = ((struct sockaddr_in)*(socketAddress)).sin_addr;
+    char *buff;
+    buff = inet_ntoa(ipAsStruct);
+    NSString *ip = [NSString stringWithUTF8String:buff];
+    return ip;
+}
+
++ (uint16_t)portFromSockAddrData:(NSData*)data {
+    struct sockaddr_in * socketAddressPtr = (struct sockaddr_in *)data.bytes;
+    struct sockaddr_in socketAddress = ((struct sockaddr_in)*(socketAddressPtr));
+    return socketAddress.sin_port;
+}
+
+@end

BitTorrent/UDP Networking/InternetProtocol.swift

@@ -0,0 +1,197 @@
+//
+//  InternetProtocol.swift
+//  BitTorrent
+//
+//  Created by Ben Davis on 03/07/2017.
+//  Copyright © 2017 Ben Davis. All rights reserved.
+//
+
+import Foundation
+
+let IOS_CELLULAR_INTERFACE_NAME = "pdp_ip0"
+let IOS_WIFI_INTERFACE_NAME = "en0"
+let IP_ADDR_IPv4_INTERFACE_NAME = "ipv4"
+let IP_ADDR_IPv6_INTERFACE_NAME = "ipv6"
+
+func ipAddress(fromSockAddrData data: Data) -> String? {
+    let socketAddress = data.withUnsafeBytes() { (pointer: UnsafePointer<sockaddr_in>) in
+        return pointer.pointee
+    }
+    guard let resultCString = inet_ntoa(socketAddress.sin_addr) else {
+        return nil
+    }
+    return String(cString: resultCString)
+}
+
+func port(fromSockAddrData data: Data) -> UInt16 {
+    let socketAddress = data.withUnsafeBytes() { (pointer: UnsafePointer<sockaddr_in>) in
+        return pointer.pointee
+    }
+    return socketAddress.sin_port
+}
+
+//    + (NSString*)ipAddressFromSockAddrData:(NSData*)data {
+//        struct sockaddr_in * socketAddress = (struct sockaddr_in *)data.bytes;
+//        struct    in_addr ipAsStruct = ((struct sockaddr_in)*(socketAddress)).sin_addr;
+//        char *buff;
+//        buff = inet_ntoa(ipAsStruct);
+//        NSString *ip = [NSString stringWithUTF8String:buff];
+//        return ip;
+//        }
+//
+//        + (uint16_t)portFromSockAddrData:(NSData*)data {
+//            struct sockaddr_in * socketAddressPtr = (struct sockaddr_in *)data.bytes;
+//            struct sockaddr_in socketAddress = ((struct sockaddr_in)*(socketAddressPtr));
+//            return socketAddress.sin_port;
+//}
+
+func getIPAddress(of hostname: String) -> String? {
+    
+    guard let hostnameCString = hostname.cString(using: .ascii),
+        let hostEntry = gethostbyname(hostnameCString)?.pointee,
+        let hostAddressList = hostEntry.h_addr_list?.pointee else {
+        return nil
+    }
+    
+    let firstHostAddress = hostAddressList.withMemoryRebound(to: in_addr.self, capacity: 1) { $0.pointee }
+    let firstHostAddressCString = inet_ntoa(firstHostAddress)!
+    return String(cString: firstHostAddressCString)
+}
+
+func getLocalIPAddress(preferIPv4: Bool = true) -> String? {
+    
+    // Prefer wifi over cellular
+    let searchArray = preferIPv4 ?
+        [
+            IOS_WIFI_INTERFACE_NAME + "/" + IP_ADDR_IPv4_INTERFACE_NAME,
+            IOS_WIFI_INTERFACE_NAME + "/" + IP_ADDR_IPv6_INTERFACE_NAME,
+            IOS_CELLULAR_INTERFACE_NAME + "/" + IP_ADDR_IPv4_INTERFACE_NAME,
+            IOS_CELLULAR_INTERFACE_NAME + "/" + IP_ADDR_IPv6_INTERFACE_NAME,
+        ] :
+        [
+            IOS_WIFI_INTERFACE_NAME + "/" + IP_ADDR_IPv6_INTERFACE_NAME,
+            IOS_WIFI_INTERFACE_NAME + "/" + IP_ADDR_IPv4_INTERFACE_NAME,
+            IOS_CELLULAR_INTERFACE_NAME + "/" + IP_ADDR_IPv6_INTERFACE_NAME,
+            IOS_CELLULAR_INTERFACE_NAME + "/" + IP_ADDR_IPv4_INTERFACE_NAME,
+        ]
+    
+    let addresses = getLocalIPAddresses()
+    
+    for searchItem in searchArray {
+        if let result = addresses[searchItem] {
+            return result
+        }
+    }
+    
+    return nil
+}
+
+func getLocalIPAddresses() -> [String: String] {
+    
+    var addresses: [String: String] = [:]
+    
+    // Get list of all network interfaces on the local machine:
+    var ifaddrsPointer : UnsafeMutablePointer<ifaddrs>?
+    guard getifaddrs(&ifaddrsPointer) == 0, let ifaddrsList = ifaddrsPointer?.pointee else {
+        return [:]
+    }
+    
+    // For each network interface ...
+    for ifaddrs in ifaddrsList {
+        if !ifaddrs.isUpAndRunning || ifaddrs.isLoopbackNet {
+            continue
+        }
+        
+        if ifaddrs.isIpv4 || ifaddrs.isIpv6 {
+            if let addressString = ifaddrs.convertToIPString(), let name = ifaddrs.nameAndTypeString() {
+                addresses[name] = addressString
+            }
+        }
+    }
+    
+    freeifaddrs(ifaddrsPointer)
+    
+    return addresses
+}
+
+public class ifaddrsIterator: IteratorProtocol {
+    public typealias Element = ifaddrs
+    
+    var nextElement: ifaddrs?
+    
+    init(first: ifaddrs) {
+        nextElement = first
+    }
+    
+    public func next() -> ifaddrs? {
+        let result = nextElement
+        nextElement = result?.ifa_next?.pointee
+        return result
+    }
+}
+
+extension ifaddrs: Sequence {
+    public func makeIterator() -> ifaddrsIterator {
+        return ifaddrsIterator(first: self)
+    }
+}
+
+extension ifaddrs {
+    
+    var name: String {
+        return String(cString: ifa_name)
+    }
+    
+    var isIpv4: Bool {
+        let addr = ifa_addr.pointee
+        return addr.sa_family == UInt8(AF_INET)
+    }
+    
+    var isIpv6: Bool {
+        let addr = ifa_addr.pointee
+        return addr.sa_family == UInt8(AF_INET6)
+    }
+    
+    var isUpAndRunning: Bool {
+        let flags = Int32(ifa_flags)
+        let upAndRunningFlags = (IFF_UP|IFF_RUNNING)
+        return (flags & upAndRunningFlags) == upAndRunningFlags
+    }
+    
+    var isLoopbackNet: Bool {
+        let flags = Int32(ifa_flags)
+        return (flags & IFF_LOOPBACK) == IFF_LOOPBACK
+    }
+    
+    func convertToIPString() -> String? {
+        return ifa_addr.pointee.toString()
+    }
+    
+    func nameAndTypeString() -> String? {
+        
+        guard isIpv4 || isIpv6 else {
+            return nil
+        }
+        
+        return "\(name) - " + (isIpv4 ? IP_ADDR_IPv4_INTERFACE_NAME : IP_ADDR_IPv6_INTERFACE_NAME)
+    }
+}
+
+extension sockaddr {
+    
+    func toString() -> String? {
+        
+        var hostname = [CChar](repeating: 0, count: Int(NI_MAXHOST))
+        var addr = self
+        
+        guard getnameinfo(&addr,
+                          socklen_t(addr.sa_len),
+                          &hostname,
+                          socklen_t(hostname.count),
+                          nil,
+                          socklen_t(0),
+                          NI_NUMERICHOST) == 0 else { return nil }
+        
+        return String(validatingUTF8: hostname)
+    }
+}

BitTorrent/UDP Networking/InternetProtocolTests.swift

@@ -0,0 +1,48 @@
+//
+//  InternetProtocolTests.swift
+//  BitTorrentTests
+//
+//  Created by Ben Davis on 03/07/2017.
+//  Copyright © 2017 Ben Davis. All rights reserved.
+//
+
+import XCTest
+@testable import BitTorrent
+
+class InternetProtocolTests: XCTestCase {
+    
+    func test_canDecodeLocalhost() {
+        let result = getIPAddress(of: "localhost")
+        XCTAssertNotNil(result)
+        XCTAssertEqual(result!, "127.0.0.1")
+    }
+    
+    func test_invalidHostnameReturnsNil() {
+        let result = getIPAddress(of: "asldfjhablskhdbj")
+        XCTAssertNil(result)
+    }
+    
+    func test_nonAsciiHostnameReturnsNil() {
+        let result = getIPAddress(of: "🙁")
+        XCTAssertNil(result)
+    }
+    
+    func test_canDecodeGoogle() {
+        let result = getIPAddress(of: "google.com")
+        XCTAssertNotNil(result)
+    }
+    
+    func test_canDecodeIPv4AddressFromData() {
+        let data = Data(bytes: [16,2,122,105,127,0,0,1,0,0,0,0,0,0,0,0])
+        let result = ipAddress(fromSockAddrData: data)
+        XCTAssertNotNil(result)
+        XCTAssertEqual(result, "127.0.0.1")
+    }
+    
+    func test_canDecodeSocketPortFromData() {
+        let data = Data(bytes: [16,2,122,105,127,0,0,1,0,0,0,0,0,0,0,0])
+        let result = port(fromSockAddrData: data)
+        XCTAssertNotNil(result)
+        XCTAssertEqual(result, 27002)
+    }
+}

BitTorrent/UDP Networking/UDPConnection.swift

@@ -0,0 +1,62 @@
+//
+//  UDPConnection.swift
+//  BitTorrent
+//
+//  Created by Ben Davis on 03/07/2017.
+//  Copyright © 2017 Ben Davis. All rights reserved.
+//
+
+import Foundation
+import CocoaAsyncSocket
+
+protocol UDPConnectionDelegate: class {
+    func udpConnection(_ sender: UDPConnection, receivedData data: Data, fromHost host: String)
+}
+
+/// This class is a thin wrapper around the socket library to protect against changes
+/// in its interface, and to allow me to replace CocoaAsyncSocket with a swift framework
+/// one day.
+class UDPConnection: NSObject {
+    
+    weak var delegate: UDPConnectionDelegate?
+    
+    private let socket: GCDAsyncUdpSocket
+    
+    // Designated init for testing
+    init(socket: GCDAsyncUdpSocket) {
+        self.socket = socket
+        super.init()
+        socket.setDelegate(self)
+        socket.synchronouslySetDelegateQueue(.main)
+    }
+    
+    // Useful init which should be used
+    override convenience init() {
+        self.init(socket: GCDAsyncUdpSocket())
+    }
+    
+    deinit {
+        socket.close()
+    }
+    
+    func startListening(on port: UInt16) {
+        try? socket.bind(toPort: port)
+        try? socket.beginReceiving()
+    }
+    
+    func send(_ data: Data, toHost host: String, port: UInt16, timeout: TimeInterval) {
+        socket.send(data, toHost: host, port: port, withTimeout: timeout, tag: 0)
+    }
+}
+
+extension UDPConnection: GCDAsyncUdpSocketDelegate {
+    
+    func udpSocket(_ sock: GCDAsyncUdpSocket,
+                   didReceive data: Data,
+                   fromAddress address: Data,
+                   withFilterContext filterContext: Any?) {
+        
+        let hostString = ipAddress(fromSockAddrData: address)!
+        delegate?.udpConnection(self, receivedData: data, fromHost: hostString)
+    }
+}

BitTorrent/UDP Networking/UDPConnectionTests.swift

@@ -0,0 +1,92 @@
+//
+//  UDPConnectionTests.swift
+//  BitTorrentTests
+//
+//  Created by Ben Davis on 03/07/2017.
+//  Copyright © 2017 Ben Davis. All rights reserved.
+//
+
+import XCTest
+import CocoaAsyncSocket
+@testable import BitTorrent
+
+class UDPConnectionDelegateTestingStub: UDPConnectionDelegate {
+    
+    var receivedDataCalled = false
+    var receivedDataParameters: (sender: UDPConnection, data: Data, host: String)?
+    func udpConnection(_ sender: UDPConnection, receivedData data: Data, fromHost host: String) {
+        receivedDataCalled = true
+        receivedDataParameters = (sender, data, host)
+    }
+}
+
+class UDPConnectionTests: XCTestCase {
+    
+    var socket: GCDAsyncUdpSocketStub!
+    var delegate: UDPConnectionDelegateTestingStub!
+    var sut: UDPConnection!
+    
+    override func setUp() {
+        super.setUp()
+        
+        socket = GCDAsyncUdpSocketStub()
+        delegate = UDPConnectionDelegateTestingStub()
+        sut = UDPConnection(socket: socket)
+        sut.delegate = delegate
+    }
+    
+    func test_isSocketDelegate() {
+        XCTAssert(socket._delegate === sut)
+        XCTAssert(socket._delegateQueue === DispatchQueue.main)
+    }
+    
+    func test_canStartListeningOnPort() {
+        
+        let port: UInt16 = 123
+        sut.startListening(on: port)
+        
+        XCTAssert(socket.bindToPortCalled)
+        XCTAssertEqual(socket.bindToPortParameter, port)
+        XCTAssert(socket.beginReceivingCalled)
+    }
+    
+    func test_socketClosedOnDeinit() {
+        sut = nil
+        XCTAssert(socket.closeCalled)
+    }
+    
+    // MARK: - Receiving data
+    
+    func test_canRecieveData() {
+        
+        // 127.0.0.1:27002
+        let addressData = Data(bytes: [16,2,122,105,127,0,0,1,0,0,0,0,0,0,0,0])
+        let packetData = Data(bytes: [1,2,3])
+        
+        sut.udpSocket(socket, didReceive: packetData, fromAddress: addressData, withFilterContext: nil)
+        
+        XCTAssert(delegate.receivedDataCalled)
+        XCTAssertEqual(delegate.receivedDataParameters?.sender, sut)
+        XCTAssertEqual(delegate.receivedDataParameters?.data, packetData)
+        XCTAssertEqual(delegate.receivedDataParameters?.host, "127.0.0.1")
+    }
+    
+    // MARK: - Sending data
+    
+    func test_canSendData() {
+        
+        let data = Data(bytes: [1,2,3])
+        let host = "127.0.0.1"
+        let port: UInt16 = 3475
+        let timeout: TimeInterval = 10
+        
+        sut.send(data, toHost: host, port: port, timeout: timeout)
+        
+        XCTAssert(socket.sendCalled)
+        XCTAssertEqual(socket.sendParameters!.data, data)
+        XCTAssertEqual(socket.sendParameters!.host, host)
+        XCTAssertEqual(socket.sendParameters!.port, port)
+        XCTAssertEqual(socket.sendParameters!.timeout, timeout)
+    }
+}
+

BitTorrentExample/AppDelegate.swift

@@ -8,14 +8,14 @@
 
 import UIKit
 @testable import BitTorrent
-import BlueSocket
 
 @UIApplicationMain
-class AppDelegate: UIResponder, UIApplicationDelegate {
+class AppDelegate: UIResponder, UIApplicationDelegate, UDPConnectionDelegate {
     
     var window: UIWindow?
     
     var tracker: TorrentHTTPTracker!
+    var udpConnection: UDPConnection!
     
     func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
         window = UIWindow(frame: UIScreen.main.bounds)
@@ -39,10 +39,26 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
 //                               numberOfBytesDownloaded: 0,
 //                               numberOfPeersToFetch: 50)
         
-        let mySocket = try! Socket.create()
+//        let mySocket = try! Socket.create()
-        print(mySocket)
+//        print(mySocket)
+        
+        udpConnection = UDPConnection()
+        udpConnection.delegate = self
+        
+        udpConnection.startListening(on: 59740)
+        
+        let data = "Hello, world!".data(using: .utf8)!
+        udpConnection.send(data, toHost: "127.0.0.1", port: 31337, timeout: 10000)
         
         return true
     }
     
 }
+
+extension UDPConnectionDelegate {
+    
+    func udpConnection(_ sender: UDPConnection, receivedData data: Data, fromHost host: String) {
+        print(sender, data, host)
+        print(data == "Hello, world!".data(using: .utf8)! ? "Success" : "Fail")
+    }
+}

Podfile

@@ -4,7 +4,7 @@ target 'BitTorrent' do
   use_frameworks!
 
   pod 'Alamofire', '4.5.0'
-  pod 'BlueSocket'
+  pod 'CocoaAsyncSocket'
   
   target 'BitTorrentTests' do
     inherit! :search_paths

Podfile.lock

@@ -1,6 +1,6 @@
 PODS:
   - Alamofire (4.5.0)
-  - BlueSocket (0.12.16)
+  - CocoaAsyncSocket (7.6.1)
   - OHHTTPStubs (6.0.0):
     - OHHTTPStubs/Default (= 6.0.0)
   - OHHTTPStubs/Core (6.0.0)
@@ -17,14 +17,14 @@ PODS:
 
 DEPENDENCIES:
   - Alamofire (= 4.5.0)
-  - BlueSocket
+  - CocoaAsyncSocket
   - OHHTTPStubs
 
 SPEC CHECKSUMS:
   Alamofire: f28cdffd29de33a7bfa022cbd63ae95a27fae140
-  BlueSocket: 13bf1daf94a316e9efe93aa125cc33b8c3dd6c35
+  CocoaAsyncSocket: 7eadd3f59e1a6c84e2aefc93e9ff7b55156fe174
   OHHTTPStubs: 752f9b11fd810a15162d50f11c06ff94f8e012eb
 
-PODFILE CHECKSUM: 0d38beb67a05d0be9e85d2555a9fbc44ecf5e80c
+PODFILE CHECKSUM: 0357d6a70a8533160f506a62590771b1f36ca2cc
 
 COCOAPODS: 1.2.0