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

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, 0.068531945200942] 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。