Sockets recvfrom重新读取套接字上的数据
我正在创建一个简单的服务器/客户端UDP套接字程序,但遇到了一个问题 问题是recvfrom()函数会不断重新读取上次发送的数据 因此,如果我从客户端向服务器发送两个数据包,那么recvfrom()将读取第一个数据包并打印其数据,然后它将不断地反复读取第二个数据包 据我所知,一旦执行了成功的读取操作,就应该将数据包从套接字中删除,但这似乎没有发生 我知道客户端没有重新发送数据,因为每当客户端发送数据时都会写入控制台输出 这是发送程序的函数Sockets recvfrom重新读取套接字上的数据,sockets,unix,udp,recvfrom,Sockets,Unix,Udp,Recvfrom,我正在创建一个简单的服务器/客户端UDP套接字程序,但遇到了一个问题 问题是recvfrom()函数会不断重新读取上次发送的数据 因此,如果我从客户端向服务器发送两个数据包,那么recvfrom()将读取第一个数据包并打印其数据,然后它将不断地反复读取第二个数据包 据我所知,一旦执行了成功的读取操作,就应该将数据包从套接字中删除,但这似乎没有发生 我知道客户端没有重新发送数据,因为每当客户端发送数据时都会写入控制台输出 这是发送程序的函数 int sendPacket(int socketFd,
int sendPacket(int socketFd, int type, char *typeString, char *data, int seq, int windowSize, struct sockaddr_in serverName) {
struct packet *sendPacketPtr, sendPacket;
fd_set writeFdSet;
sendPacketPtr = &sendPacket;
sendPacket.flags = type;
sendPacket.windowsize = windowSize;
sendPacket.seq = seq;
sendPacket.id = getpid();
if (type == NORMAL)
strcpy(sendPacket.data, data);
FD_ZERO(&writeFdSet);
FD_SET(socketFd, &writeFdSet);
if(select(FD_SETSIZE, NULL, &writeFdSet, NULL, NULL) > 0) {
if(sendto(socketFd, sendPacketPtr, sizeof(sendPacket), 0, (struct sockaddr *)&serverName, sizeof(serverName)) < 0) {
printf("%s packet was not sent\n", typeString);
perror("Send error");
} else {
printf("%s packet was sent\n", typeString);
}
}
return 0;
}
永远运行的输出(因为它一直在重新读取最后一个数据包)是:
然后,只有您正在打印缓冲区并再次调用该函数 在“receivePacket”功能中,明确选择超时或recvfrom故障 将“receivedPacket.flags”更新为otherthen NORMAL,这样您就可以在执行循环时 休息
在执行任何其他系统调用(如write())之前,必须先调用peror(),这是由printf()调用的。否则,errno值可能会更改,您会打印误导性的错误消息。我尝试了第二个答案,但没有成功。”Memsetting'buffer为0确实有效,同时也消除了我遇到的一些其他问题。谢谢这不是第二个答案,你需要注意上面提到的两点(1和2)
for (int i = seqBase; i <= seqMax && i < packetNum; i++) {
sendPacket(socketFd, NORMAL, "DATA", dataArray[i], i, 0, serverName);
}
struct packet receivePacket (int socketFd, struct sockaddr_in *address, int timeout, int useTimeout) {
struct packet buffer;
fd_set readFdSet;
struct sockaddr_in dest_addr;
struct timeval selectTimeout;
selectTimeout.tv_usec = 0;
selectTimeout.tv_sec = timeout;
FD_ZERO(&readFdSet);
FD_SET(socketFd, &readFdSet);
socklen_t len = sizeof(dest_addr);
if(useTimeout == 0) {
if(select(FD_SETSIZE, &readFdSet, NULL, NULL, NULL) > 0) {
if(recvfrom(socketFd, &buffer, sizeof(buffer), 0, (struct sockaddr *)&dest_addr, &len) < 0) {
perror("Read error");
}else {
*address = dest_addr;
}
}
}else {
if(select(FD_SETSIZE, &readFdSet, NULL, NULL, &selectTimeout) > 0) {
if(recvfrom(socketFd, &buffer, sizeof(buffer), 0, (struct sockaddr *)&dest_addr, &len) < 0) {
perror("Read error");
}else {
*address = dest_addr;
}
}
}
return buffer;
}
receivedPacket = receivePacket(socketFd, &destAddress, 0, 0);
while (receivedPacket.flags == NORMAL) {
printf("Data received: \"%s\", sequence: %d\n", receivedPacket.data, receivedPacket.seq);
receivedPacket = receivePacket(socketFd, &destAddress, TIMEOUT, 1);
}
Data received: "Packet 0", sequence: 0
Data received: "Packet 1", sequence: 1
Data received: "Packet 1", sequence: 1
Data received: "Packet 1", sequence: 1
Data received: "Packet 1", sequence: 1
........