commit acec768a9a92d4b31db8e9884b0ccf5df173ec1b
Author: Josh Holtrop <jholtrop@gmail.com>
Date:   Fri May 22 22:13:24 2020 -0400

    add source

diff --git a/tttt.rb b/tttt.rb
new file mode 100644
index 0000000..5f771f3
--- /dev/null
+++ b/tttt.rb
@@ -0,0 +1,104 @@
+require "socket"
+
+@server = TCPServer.new(5678)
+@players = [@server.accept, @server.accept]
+@labels = %w[X O]
+@board = [[nil] * 3, [nil] * 3, [nil] * 3]
+@turn = 0
+@winner = nil
+
+def write(msg)
+  @players[@turn].write(msg)
+end
+
+def print_board
+  position = 0
+  3.times do |y|
+    write("+---+---+---+\r\n")
+    3.times do |row|
+      3.times do |x|
+        last = x == 2 ? "|\r\n" : ""
+        case row
+        when 0
+          position = y * 3 + x + 1
+          write("|#{position}  #{last}")
+        when 1
+          entry = @board[y][x] || " "
+          write("| #{entry} #{last}")
+        when 2
+          write("|   #{last}")
+        end
+      end
+    end
+  end
+  write("+---+---+---+\r\n")
+end
+
+def get_selection
+  loop do
+    write("Select a position:\r\n")
+    input = @players[@turn].gets
+    position = input.to_i
+    if position >= 1 && position <= 9
+      y = (position - 1) / 3
+      x = (position - 1) % 3
+      return x, y if @board[y][x].nil?
+    end
+  end
+end
+
+def take_turn
+  print_board
+  x, y = get_selection
+  @board[y][x] = @labels[@turn]
+  print_board
+end
+
+def check_win_row(y)
+  if @board[y][0] && @board[y][0] == @board[y][1] && @board[y][0] == @board[y][2]
+    return @board[y][0]
+  end
+end
+
+def check_win_col(x)
+  if @board[0][x] && @board[0][x] == @board[1][x] && @board[0][x] == @board[2][x]
+    return @board[0][x]
+  end
+end
+
+def check_end
+  3.times do |i|
+    if @winner = check_win_row(i)
+      return
+    elsif @winner = check_win_col(i)
+      return
+    end
+  end
+  if @board[0][0] && @board[0][0] == @board[1][1] && @board[0][0] == @board[2][2]
+    return @winner = @board[0][0]
+  end
+  if @board[0][2] && @board[0][2] == @board[1][1] && @board[0][2] == @board[2][0]
+    return @winner = @board[0][2]
+  end
+end
+
+def print_end
+  if @winner
+    win_msg = "#{@winner} wins!"
+  else
+    win_msg = "Tie game!"
+  end
+  @players.each do |client|
+    client.write("Game over. #{win_msg}\r\n")
+  end
+end
+
+9.times do
+  take_turn
+  @turn ^= 1
+  check_end
+  break if @winner
+end
+
+print_board
+print_end