Parallel Socket Communication in Swift

https://tryswift.jp/2024

1. @S_Shimotori - try! Swift Tokyo 2024 Parallel Socket Communication in Swift
2. S_Shimotori iOS Engineer @ LY Corporation Eventer 2
3. 3 at try! Swift Tokyo Meetup 2023/01/21 Sat.
4. From Application to Hardware Kernel Application Hardware Standard Libraries iOS application, macOS application, … URL, URLSession Socket Network interface 4 Lower
5. From Application to Hardware Kernel Hardware Standard Libraries iOS application, macOS application, … URL, URLSession Socket Network interface 5 Application
6. Parallel Socket Communication in Swift 6
7. Inter-Process Communication Process A Process B 7
8. Socket Communication Process B Socket Process A Socket 8 Host A Host B
9. Sample: Ping $ ping -c 2 example.com PING example.com (93.184.216.34): 56 data bytes 64 bytes from 93.184.216.34: icmp_seq=0 ttl=52 time=165.910 ms 64 bytes from 93.184.216.34: icmp_seq=1 ttl=52 time=108.211 ms --- example.com ping statistics --- 2 packets transmitted, 2 packets received, 0.0% packet loss round-trip min/avg/max/stddev = 108.211/137.060/165.910/28.850 ms 9
10. Sample: Ping $ ping -c 2 example.com PING example.com (93.184.216.34): 56 data bytes 64 bytes from 93.184.216.34: icmp_seq=0 ttl=52 time=165.910 ms 64 bytes from 93.184.216.34: icmp_seq=1 ttl=52 time=108.211 ms --- example.com ping statistics --- 2 packets transmitted, 2 packets received, 0.0% packet loss round-trip min/avg/max/stddev = 108.211/137.060/165.910/28.850 ms 10 byte count IP address sequence No. TTL elapsed time
11. Communication with Ping 64 bytes from 93.184.216.34: icmp_seq=0 ttl=52 time=165.910 ms 56 bytes message icmp_seq=0 64 bytes message icmp_seq=0 93.184.216.34 11
12. Interface of Serial Ping in Swift func ping( identifier: UInt16, sequenceNumber: UInt16, to address: String ) async throws -> Result data including elapsed time 12
13. Let’s dive into socket communication! 13
14. Break Down Goals into Tasks • Create a datagram socket • Encode/Decode a message • Execute system calls for messaging 14
15. Break Down Goals into Tasks • Create a datagram socket • Encode/Decode a message • Execute system calls for messaging 15
16. Datagram Socket Process Datagram Socket 16 Your computer Destination host
17. Socket on Swift let fileDescriptor: Int32 = Foundation.socket(…) 17
18. Socket on Swift let fileDescriptor: Int32 = Foundation.socket(…) sendto(fileDescriptor, …) recvfrom(fileDescriptor, …) 18
19. Socket on Swift let fileDescriptor: Int32 = Foundation.socket(…) sendto(fileDescriptor, …) recvfrom(fileDescriptor, …) close(fileDescriptor) 19
20. Socket on Swift let fileDescriptor: Int32 = Foundation.socket(…) sendto(fileDescriptor, …) recvfrom(fileDescriptor, …) close(fileDescriptor) sendto(fileDescriptor, …) // runtime error 20
21. Socket on Swift ‘ fi leDescriptor' used after consume let fileDescriptor = FileDescriptor(fd: socket(…)) fileDescriptor.send(…) fileDescriptor.receive(…) fileDescriptor.close() // consuming func fileDescriptor.send(…) 21 struct FileDescriptor: ~Copyable
22. Break Down Goals into Tasks • Create a datagram socket ✅ • Encode/Decode a message • Execute system calls for messaging 22
23. 00001000 00000000 11110111 11110110 00000000 00000100 00000000 00000101 …… Binary Message Data for Ping 23
24. Binary Message Data for Ping type code checksum identi fi er sequence number 00001000 00000000 11110111 11110110 00000000 00000100 00000000 00000101 …… 24
25. Using Structure to Encode Message struct ICMPEchoRequest { let type: UInt8 let code: UInt8 let checksum: UInt16 let identifier: UInt16 let sequenceNumber: UInt16 …… } 00001000 00000000 11110111 11110110 00000000 00000100 00000000 00000101 …… 25
26. Byte Order • Big endian, in network 00000000 00000101 = 5 • Little endian, in Swift 00000101 00000000 = 0b101 = UInt16(5) 00000000 00000101 = 0b101_00000000 = UInt16(1280) 00000000 00000101 = UInt16(5).bigEndian = UInt16(1280) 26
27. Using Structure to Decode Received Message struct IPv4Header { …… let timeToLive: UInt8 …… let sourceIPAddress: in_addr …… } …… 01000000 …… 01111111 00000000 00000000 00000001 …… 27
28. Break Down Goals into Tasks • Create a datagram socket ✅ • Encode/Decode a message ✅ • Execute system calls for messaging 28
29. System Calls for Datagram Socket • sendto(…, UnsafeRawPointer, …) -> length of message • poll(…, Int32) -> result • recvfrom(…, UnsafeMutableRawPointer, …) -> length of message pointer to Data pointer to Data for storing timeout 29
30. System Call with Unsafe Types message.withUnsafeBytes { pointerToMessage in withUnsafePointer(to: address) { pointerToAddress in sendto(…, UnsafeRawPointer, …, UnsafePointer<sockaddr>, …) } } 30
31. Poll before Receive // These functions block until receiving _ = poll(…, Int32) _ = recvfrom(…, UnsafeMutableRawPointer, …) timeout 31 mutable Data
32. Break Down Goals into Tasks • Create a datagram socket ✅ • Encode/Decode a message ✅ • Execute system calls for messaging ✅ 32
33. Datagram Socket Data Flow of “Serial” Ping Timer UI Data Binding 33 Your computer Destination host every sec.
34. Advanced: Parallel Requests 34
35. Monitoring Multiple Hosts 35
36. Monitoring Multiple Hosts 36 deadman
37. Multiple Request Messages Datagram Socket Host A Host B Host C 37 ping Your computer
38. Multiple Reply Messages Datagram Socket Host A Host B Host C 38 reply Your computer
39. Multiple Reply Messages Datagram Socket Host A Host B Host C 39 reply Your computer Timers UI Data Binding while true { poll(…) } timeout cancel Timer every sec.
40. Logic that We Should Code in Swift • Sorting received messages • Handling timeout 40
41. Supplement: About ncurses • Thread-unsafe • Managing screens using OpaquePointer 41
43. Summary • You can experience socket communication using Swift. • Swift ensures safety and helps parallel communication. • Have fun learning socket communication with Swift! 43
44. 44 @S_Shimotori_pub @S-Shimotori
45. References 45
46. Official Pages • API Reference: iOS Manual Pages • https://developer.apple.com/library/archive/documentation/System/Conceptual/ ManPages_iPhoneOS/index.html • Unsafe Swift - WWDC20 - Videos - Apple Developer • https://developer.apple.com/videos/play/wwdc2020/10648 • Safely manage pointers in Swift - WWDC20 - Videos - Apple Developer • https://developer.apple.com/videos/play/wwdc2020/10167/ • swift-evolution/proposals/0390-noncopyable-structs-and-enums.md at main · apple/swift- evolution • https://github.com/apple/swift-evolution/blob/main/proposals/0390-noncopyable-structs-and- enums.md 46
47. apple/swift - Int.bigEndian • swift/stdlib/public/core/Integers.swift at d7b3d3e319d99ee3956dd1af899b73112d7517fd · apple/swift • https://github.com/apple/swift/blob/d7b3d3e319d99ee3956dd1af899b73112d7517fd/stdlib/public/core/ Integers.swift#L2296-L2321 • swift/stdlib/public/core/IntegerTypes.swift.gyb at 633d5bc45a7c0a7b0e481701cf3f8fc2025f8f51 · apple/swift • https://github.com/apple/swift/blob/633d5bc45a7c0a7b0e481701cf3f8fc2025f8f51/stdlib/public/core/ IntegerTypes.swift.gyb#L1646-L1654 • llvm-project/llvm/include/llvm/IR/Intrinsics.td at 11fcae69dbea4860e20ab799ecca9b0432d7f19d · llvm/llvm- project • https://github.com/llvm/llvm-project/blob/11fcae69dbea4860e20ab799ecca9b0432d7f19d/llvm/include/ llvm/IR/Intrinsics.td#L638-L641 • LLVM Language Reference Manual &#8212; LLVM 19.0.0git documentation • https://llvm.org/docs/LangRef.html#id664 47
48. System Programming • Kerrisk, Michael. The Linux Programming Interface. No Starch Press. • ઍॅ࣏࿠ ༁. LinuxϓϩάϥϛϯάΠϯλϑΣʔε. ΦϥΠϦʔɾδϟύϯ • UNIXωοτϫʔΫϓϩάϥϛϯάʹొ৔͢Δߏ଄ମͷ঺հͱਖ਼͍͠࢖͍ํ • “Introduction and proper use of structures in UNIX network programming” • http://cms.phys.s.u-tokyo.ac.jp/~naoki/CIPINTRO/NETWORK/struct.html 48
49. Ping • upa/deadman: deadman is a curses-based host status checking application using ping • https://github.com/upa/deadman • Ping͕OKͱͳΔ৚݅ʢҟͳΔΞυϨε͔ΒԠ౴͕ฦ͖ͬͯͨ৔߹ʣ • “Conditions under which a ping is fine (when a response is returned from a different address)” • https://infrastructure-engineer.com/tcpip-basic-0005/ • ICMPͷNAPTӽ͑-ϙʔτ൪߸͕ͳ͍ͷʹͳͥʁ | izuminͷඋ๨࿥ • “ICMP through NAT traversal-Why it can pass without a port number” • https://izuminmin.com/network/icmpping-napt/ 49
50. Resources 50
51. Image Resources • ͔Θ͍͍ϑϦʔૉࡐू ͍Β͢ͱ΍ • https://www.irasutoya.com/ • About X | Our logo, brand guidelines, and tools • https://about.x.com/en/who-we-are/brand-toolkit • GitHub Logos and Usage • https://github.com/logos 51