需求
有时候我们需要有几个不同的master, 他们之间要交换topic的内容，这时候就不能使用ros自带的设置同一个master的方法.
我们的处理方法是，构造一个client和一个server，他们运行在不同的master下面, client在master1下订阅topic1，然后通过tcp协议(自己定义一个消息协议格式)发到master2下面的server,进行消息解析，再发布出master2下面的topic1，这样我们不改变ros自带的topic框架，就实现topic1的消息从master1到master2的传播.
下面我们实现的是将一个amcl_pose的topic，消息类型是PoseWithCovarianceStamped从master1传到master2，其他的topic代码类似
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client 的代码
#! /usr/bin/env python# -*- coding=utf-8 -*-import socketimport structimport rospyimport timefrom geometry_msgs.msg import PoseWithCovarianceStamped,PoseStamped#message proto# id | length | datadef send_msg(sock, msg ,id):
# Prefix each message with a 4-byte id and length (network byte order)
msg = struct.pack('>I',int(id)) + struct.pack('>I', len(msg)) + msg
sock.sendall(msg)def odomCallback(msg):
global odom_socket
data = ""
id = msg.header.seq print "send id: ",id
x = msg.pose.pose.position.x
y = msg.pose.pose.position.y #orientation
orien_z = msg.pose.pose.orientation.z
orien_w = msg.pose.pose.orientation.w
data += str(x) + "," + str(y)+ "," + str(orien_z)+ "," + str(orien_w)
send_msg(odom_socket,data,id)
odom_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
odom_socket.connect(('127.0.0.1',8000))
rospy.init_node('server_node')
rospy.Subscriber('/amcl_pose',PoseWithCovarianceStamped,odomCallback)
rospy.spin()server 的代码
#! /usr/bin/env python# -*- coding=utf-8 -*-import socketimport time,os,fcntlimport structimport rospyfrom geometry_msgs.msg import PoseWithCovarianceStamped,PoseStamped#message proto# id | length | datadef recv_msg(sock):
try: # Read message length and unpack it into an integer
raw_id = recvall(sock, 4) if not raw_id: return None
id = struct.unpack('>I', raw_id)[0] print "receive id: ",id
raw_msglen = recvall(sock, 4) if not raw_msglen: return None
msglen = struct.unpack('>I', raw_msglen)[0] # Read the message data
return recvall(sock, msglen) except Exception ,e: return Nonedef recvall(sock, n):
# Helper function to recv n bytes or return None if EOF is hit
data = ''
while len(data) < n:
packet = sock.recv(n - len(data)) if not packet: return None
data += packet return data##把接受的数据重新打包成ros topic发出去def msg_construct(data):
list = data.split(',')
pose = PoseWithCovarianceStamped()
pose.header.stamp = rospy.Time.now()
pose.header.frame_id = "/map"
pose.pose.pose.position.x = float(list[0])
pose.pose.pose.position.y = float(list[1])
pose.pose.pose.position.z = 0
pose.pose.pose.orientation.x = 0
pose.pose.pose.orientation.y = 0
pose.pose.pose.orientation.z = float(list[2])
pose.pose.pose.orientation.w = float(list[3])
pose.pose.covariance = [0.25, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.25, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.06853891945200942] return pose#初始化socket，监听8000端口odom_socket = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
odom_socket.bind(('',8000))
odom_socket.listen(10)
(client,address) = odom_socket.accept()
rospy.init_node("client_node")
odom_pub = rospy.Publisher("/amcl_pose",PoseWithCovarianceStamped,queue_size=30)
r = rospy.Rate(1000)#设置noblock，否则会阻塞在接听，下面while不会一直循环，只有在有数据才进行下一次循环fcntl.fcntl(client, fcntl.F_SETFL, os.O_NONBLOCK)while not rospy.is_shutdown():
data = recv_msg(client) if data:
odom_pub.publish(msg_construct(data))
r.sleep()结论
上面的代码在局域网内测试过，发送图像，激光的数据都可以保证不丢数据。
