A simple tcp server demo which implements a application-level protocal based on tcp protocal.
totalLength(4)|data(n)
| segment | type | size | remark |
| ---------- | ------ | ------- | ----------------------- |
| `dataSize` | int32 | 4 | the size of `data` only |
| `data` | []byte | dynamic | |
totalLength(4)|data(n)
| segment | type | size | remark |
| ---------- | ------ | ------- | ----------------------- |
| `commandId`| byte | 1 | message type |
| `id` | int64 | 8 | message id |
| `payload` | []byte | dynamic | |
$ make
$ ./server
$ ./client