尝试在 java 中使用 protobuf 发送和接收消息，但出现错误：协议消息包含无效标签（零）
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Trying to send and receive message using protobuf in java,but got error: Protocol message contained an invalid tag (zero)
提问by Ryan Zhu
The problem happened at server end, parseDelimitedFrom() calling.
问题发生在服务器端， parseDelimitedFrom() 调用。
Client End:
客户端：
C2SGainCard.Builder s = C2SGainCard.newBuilder();
C2SGainCard c2s = s.build();
GameRequest.Builder reqBuilder=GameRequest.newBuilder();
reqBuilder.setBody(c2s.toByteString());
reqBuilder.setName(C2SGainCard.class.getSimpleName());
reqBuilder.setPlayerId("3");
GameRequest request=reqBuilder.build();
DataOutputStream os = new DataOutputStream(socket.getOutputStream());
os.write(request.toByteArray());
os.flush();
os.close();
socket.close();
Server End:
服务器端：
try{
DataInputStream is = new DataInputStream(socket.getInputStream());
GameRequest gameRequest = GameRequest.parseDelimitedFrom(is);
}catch(Exception ex){
System.out.println(ex.getMessage());
}
And here is the another similar question:
这是另一个类似的问题：
Client End:
客户端：
C2SSell.Builder s = C2SSell.newBuilder();
CardOnSell.Builder cardOnSell = CardOnSell.newBuilder();
cardOnSell.setId(1);
cardOnSell.setPlayerId(3);
cardOnSell.setCardId(1);
cardOnSell.setCurrentPrice(111);
cardOnSell.setFixedPrice(555);
cardOnSell.setDescription("cao");
s.setCardOnSell(cardOnSell.build());
C2SSell c2s = s.build();
socket processing was the same.
套接字处理是相同的。
Server End:
服务器端：
DataInputStream is = new DataInputStream(socket.getInputStream());
byte[] b = new byte[1024];
int len=is.read(b);
String as = new String(b, 0, len);
GameRequest gameRequest=GameRequest.parseFrom(as.getBytes());
Turns out that the server end will break at the parseFrom() calling again.But when I comment two lines:
原来服务器端会在 parseFrom() 再次调用时中断。但是当我评论两行时：
cardOnSell.setCurrentPrice(111);
cardOnSell.setFixedPrice(555);
on the client End,the parseFrom() calling just worked without problem. At frist I suspected the .proto file has some problems and it's been proved there is no problem there... So how does this problem come? It that because I miss some data before the parseFrom() calling?
在客户端， parseFrom() 调用刚刚工作没有问题。一开始我怀疑.proto文件有问题，后来证明没有问题……那么这个问题是怎么来的呢？是因为我在 parseFrom() 调用之前错过了一些数据吗？
采纳答案by Jon Skeet
I can't remember exactly what format parseDelimitedFromexpects, but I suspectyou just want parseFromin your server side.
我不记得确切的格式parseDelimitedFrom需要什么，但我怀疑你只是想parseFrom在你的服务器端。
It's not clear why you're using os.write(request.toByteArray())though, or indeed why you're creating a DataOutputStream. You should be able to use just OutputStreamand InputStream, writing:
目前尚不清楚您为什么要使用os.write(request.toByteArray())，或者您为什么要创建DataOutputStream. 你应该能够使用 just OutputStreamand InputStream，写作：
request.writeTo(socket.getOutputStream());
and then:
接着：
GameRequest gameRequest = GameRequest.parseFrom(socket.getInputStream());
If you dowant the delimited version, you need to use writeDelimitedToinstead.
如果您确实需要分隔版本，则需要writeDelimitedTo改用。
