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我想通过 pywebkitgtk 捕获网页。我在那台机器上安装了 X org 服务器，启动了 X 服务器，但出现了一些异常，但 X 服务器正在运行。问题是我无法从 X unix 套接字读取任何数据，它是 PF_FILE 类型，path=@"/tmp/.X11-unix/X0"，recvfrom 抛出 EAGAIN（资源暂时不可用）错误，轮询该套接字在没有任何数据的情况下不断超时，下面是跟踪日志，我们可以在其中找到使用 fd 5 成功创建的 unix 套接字，连接 unix 套接字，到目前为止成功，但未能从该 unix 套接字读取任何内容。

developer@kernel: /data/play/null> strace python ../pywebkitgtk-1.1.8/demos/browser.py

socket(PF_FILE, SOCK_STREAM|SOCK_CLOEXEC, 0) = 5
connect(5, {sa_family=AF_FILE, path=@"/tmp/.X11-unix/X0"}, 20) = 0
getpeername(5, {sa_family=AF_FILE, path=@"/tmp/.X11-unix/X0"}, [20]) = 0


...........................


recvfrom(5, "\1\3\304\1\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", 4096, 0, NULL, NULL) = 32
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=5, revents=POLLOUT}])
writev(5, [{"\220\10\7\0\0\1G\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0 \1", 28}, {NULL, 0}, {"", 0}], 3) = 28
poll([{fd=5, events=POLLIN}], 1, -1)    = 1 ([{fd=5, revents=POLLIN}])
recvfrom(5, "\1\3\305\1X\4\0\0\0\0\10\377G\0\0\31\31\0104\1\370\0\0\0\0\0\0\0\0\0\0\10"..., 4096, 0, NULL, NULL) = 4096
recvfrom(5, "\216\377\10\20\0\0\0\0\1\1\1\0\33\377\10\20\0\0\0\0\1\1\1\0_\377\10\20\0\0\0\0"..., 384, 0, NULL, NULL) = 384
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=5, revents=POLLOUT}])
writev(5, [{"\220\21\3\0\3\0G\0\0\30\0\0", 12}, {NULL, 0}, {"", 0}], 3) = 12
poll([{fd=5, events=POLLIN}], 1, -1)    = 1 ([{fd=5, revents=POLLIN}])
recvfrom(5, "\1\3\306\1\16\0\0\0\0\30\0\0\10\377\31\1\377\37\10\370\0\0\0\0\0\0\0\0\0\0\0\0"..., 4096, 0, NULL, NULL) = 88
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=5, revents=POLLOUT}])
writev(5, [{"\20\0\3\0\4\0G\0Meta", 12}, {NULL, 0}, {"", 0}], 3) = 12
poll([{fd=5, events=POLLIN}], 1, -1)    = 1 ([{fd=5, revents=POLLIN}])
recvfrom(5, "\1\0\307\1\0\0\0\0\206\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 4096, 0, NULL, NULL) = 32
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=5, revents=POLLOUT}])
writev(5, [{"\20\0\4\0\5\0G\0Super\0\0\0", 16}, {NULL, 0}, {"", 0}], 3) = 16
poll([{fd=5, events=POLLIN}], 1, -1)    = 1 ([{fd=5, revents=POLLIN}])
recvfrom(5, "\1\0\310\1\0\0\0\0\207\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 4096, 0, NULL, NULL) = 32
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=5, revents=POLLOUT}])
writev(5, [{"\20\0\4\0\5\0G\0Hyper\0\0\0", 16}, {NULL, 0}, {"", 0}], 3) = 16
poll([{fd=5, events=POLLIN}], 1, -1)    = 1 ([{fd=5, revents=POLLIN}])
recvfrom(5, "\1\0\311\1\0\0\0\0\210\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 4096, 0, NULL, NULL) = 32
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=5, revents=POLLOUT}])
writev(5, [{";\3\5\0\16\0 \1\0\0\0\0\3\0\3\0\316\2\22\0008\0\5\0\16\0 \1\0000\0\0"..., 16384}, {NULL, 0}, {"", 0}], 3) = 16384
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=5, revents=POLLOUT}])
writev(5, [{"6\3\2\0f\0 \1", 8}, {NULL, 0}, {"", 0}], 3) = 8
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=6, events=POLLIN}, {fd=5, events=POLLIN}], 2, 0) = 0 (Timeout)
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=6, events=POLLIN}, {fd=5, events=POLLIN}], 2, 0) = 0 (Timeout)
poll([{fd=5, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=5, revents=POLLOUT}])
writev(5, [{"5\30\4\0\200\0 \1\3\0 \1\316\2\22\0\223\4\5\0\201\0 \1\200\0 \1)\0\0\0"..., 296}, {NULL, 0}, {"", 0}], 3) = 296
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=6, events=POLLIN}, {fd=5, events=POLLIN}], 2, 497) = 0 (Timeout)
poll([{fd=5, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=5, revents=POLLOUT}])
writev(5, [{"(\30\4\0\3\0 \1\1\1\0\0\0\0\0\0", 16}, {NULL, 0}, {"", 0}], 3) = 16
poll([{fd=5, events=POLLIN}], 1, -1)    = 1 ([{fd=5, revents=POLLIN}])
recvfrom(5, "\1\1#\2\0\0\0\0\250\3\300\0o\0N\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 4096, 0, NULL, NULL) = 32
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=6, events=POLLIN}, {fd=5, events=POLLIN}], 2, 4498) = 0 (Timeout)
futex(0x7f2d8af5ea9c, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0x7f2d8af5ea98, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 1}) = 1
recvfrom(5, 0x25ff6c4, 4096, 0, 0, 0)   = -1 EAGAIN (Resource temporarily unavailable)
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2 回答 2

2

....在套接字被标记为非阻塞的部分的某个地方，因此获取EAGAIN（与 , 顺便说一句的errno(3)值相同EWOULDBLOCK）是完全正常的 - 这意味着在那个特定时刻没有数据可以消耗。

然后你的跟踪确实表明你每次都从套接字获取数据poll(2)with revents=POLLIN，所以我在这里看不到任何问题。也许只是不成功的读取总是重复两次的事实，但这不是一个真正的问题，只是效率低下（或者可能反过来——一些非常聪明的技巧）。

于 2013-05-29T15:57:59.433 回答
0

您是否在期望得到回复的 Unix 套接字上发送了 X11 协议请求？在最初的 X11 协议握手之后，除非您请求它，否则您不会从 X 服务器获得任何东西——无论是通过返回立即响应的请求，还是为以后的事件注册您的请求。

X11 协议非常复杂，尝试编写自己的代码来连接它是一项比任何人都应该做的大得多的任务——您应该使用 libxcb 或 libX11 库为您处理协议，以及更高级别的工具包，例如 GTK或 Qt 来处理大多数小部件和用户界面。

于 2013-06-02T04:47:20.217 回答