How to send an image correctly via Socket in Python

I'm trying to send an image from the 'dir' directory to another client in my network. Sockets are working properly, the image arrives at the destination and is saved, but when I try to open it I get: "This is not a valid bitmap file."

    #Código do rementente
    with open(dir, 'rb') as f:
        bits = f.read(2048)
        aux3 = len(bits)
        s.sendall(bits.encode('utf-8'))
        while aux3 < tam:
            if bits != '':
                #bits = base64.b64encode(f.read(2048))
                s.sendall(bits.encode('utf-8'))
                time.sleep(0.5)
                aux3 += len(bits)
            else:
                break
    f.close()

Here's the other part:

 #Código do Destinatário
           with open(nome, 'wb') as f:
                while x < tam:
                    try:
                        arq = s.recv(2048)
                        x += len(arq)
                        arq = arq.decode('utf-8')
                        print 'Receebndo a imagem.'
                        print 'Receebndo a imagem..'
                        print 'Receebndo a imagem...'
                        # arq1 = base64.b64decode(arq)
                        #arq = arq.decode('base64')
                        f.write(arq)
                    except Exception as e:
                        print e
                        pass
                print 'Arquivo recebido com sucesso'
                f.close()