Attempt to socket connect before establishing websocket connection

Summary:
^

Changelog: Check if there's a process listening at the specified port before attempting to establish a websocket connection on iOS

Reviewed By: fabiomassimo

Differential Revision: D35546817

fbshipit-source-id: 92ccca9afd8bcdc6d79205cc277ac813e0999166

iOS/FlipperKit/FlipperPlatformWebSocket.mm

@@ -10,6 +10,10 @@
 #import "FlipperPlatformWebSocket.h"
 #import <Flipper/Log.h>
 #import <SocketRocket/SocketRocket.h>
+#include <netdb.h>
+#include <stdio.h>
+#include <sys/socket.h>
+#include <unistd.h>
 
 static constexpr int connectionKeepaliveSeconds = 10;
 
@@ -140,6 +144,57 @@ static constexpr int connectionKeepaliveSeconds = 10;
     return;
   }
 
+  // Before attempting to establish a connection, check if
+  // there is a process listening at the specified port.
+  // CFNetwork seems to be quite verbose when the host cannot be reached
+  // causing unnecessary and annoying logs to be printed to the console.
+  struct addrinfo hints;
+
+  memset(&hints, 0, sizeof(hints));
+  hints.ai_family = AF_UNSPEC;
+  hints.ai_socktype = SOCK_STREAM;
+  hints.ai_flags = AI_PASSIVE;
+  struct addrinfo* address;
+  getaddrinfo(
+      _url.host.UTF8String, _url.port.stringValue.UTF8String, &hints, &address);
+
+  int sfd =
+      socket(address->ai_family, address->ai_socktype, address->ai_protocol);
+
+  fcntl(sfd, F_SETFL, O_NONBLOCK);
+  connect(sfd, address->ai_addr, address->ai_addrlen);
+
+  fd_set fdset;
+  struct timeval tv;
+
+  FD_ZERO(&fdset);
+  FD_SET(sfd, &fdset);
+  // Set a timeout of 3 seconds.
+  tv.tv_sec = 3;
+  tv.tv_usec = 0;
+
+  bool listening = false;
+  if (select(sfd + 1, NULL, &fdset, NULL, &tv) == 1) {
+    int so_error;
+    socklen_t len = sizeof so_error;
+
+    getsockopt(sfd, SOL_SOCKET, SO_ERROR, &so_error, &len);
+
+    if (so_error == 0) {
+      listening = true;
+    }
+    // If there's an error, most likely there is no process
+    // listening at the specified host/port (ECONNREFUSED).
+  }
+
+  freeaddrinfo(address);
+  close(sfd);
+
+  if (!listening) {
+    _eventHandler(facebook::flipper::SocketEvent::ERROR);
+    return;
+  }
+
   self.socket = [[SRWebSocket alloc] initWithURL:_url securityPolicy:_policy];
   [_socket setDelegate:self];
   [_socket open];