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, 0.06853891945200942] 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。